Buggy Python Code: The 10 Most Common Mistakes That Python Developers Make

Buggy Python Code: The 10 Most Common Mistakes That Python Developers Make

Buggy Python Code: The 10 Most Common Mistakes That Python Developers Make - Python's simple, easy-to-learn syntax can mislead Python developers — especially those who are newer to the language...

Buggy Python Code: The 10 Most Common Mistakes That Python Developers Make - Python's simple, easy-to-learn syntax can mislead Python developers — especially those who are newer to the language...

About Python

Python is an interpreted, object-oriented, high-level programming language with dynamic semantics. Its high-level built in data structures, combined with dynamic typing and dynamic binding, make it very attractive for Rapid Application Development, as well as for use as a scripting or glue language to connect existing components or services. Python supports modules and packages, thereby encouraging program modularity and code reuse.

About this article

Python’s simple, easy-to-learn syntax can mislead Python developers – especially those who are newer to the language – into missing some of its subtleties and underestimating the power of the diverse Python language.

With that in mind, this article presents a “top 10” list of somewhat subtle, harder-to-catch mistakes that can bite even some more advanced Python developers in the rear.

(Note: This article is intended for a more advanced audience than Common Mistakes of Python Programmers, which is geared more toward those who are newer to the language.)

Common Mistake #1: Misusing expressions as defaults for function arguments

Python allows you to specify that a function argument is optional by providing a default value for it. While this is a great feature of the language, it can lead to some confusion when the default value is mutable. For example, consider this Python function definition:

>>> def foo(bar=[]):        # bar is optional and defaults to [] if not specified
...    bar.append("baz")    # but this line could be problematic, as we'll see...
...    return bar

A common mistake is to think that the optional argument will be set to the specified default expression each time the function is called without supplying a value for the optional argument. In the above code, for example, one might expect that calling foo() repeatedly (i.e., without specifying a bar argument) would always return 'baz', since the assumption would be that each time foo() is called (without a bar argument specified) bar is set to [] (i.e., a new empty list).

But let’s look at what actually happens when you do this:
>>> foo()
["baz"]
>>> foo()
["baz", "baz"]
>>> foo()
["baz", "baz", "baz"]

Huh? Why did it keep appending the default value of "baz" to an existing list each time foo() was called, rather than creating a new list each time?

The more advanced Python programming answer is that the default value for a function argument is only evaluated once, at the time that the function is defined. Thus, the bar argument is initialized to its default (i.e., an empty list) only when foo() is first defined, but then calls to foo() (i.e., without a bar argument specified) will continue to use the same list to which bar was originally initialized.

FYI, a common workaround for this is as follows:

>>> def foo(bar=None):
...    if bar is None:		# or if not bar:
...        bar = []
...    bar.append("baz")
...    return bar
...
>>> foo()
["baz"]
>>> foo()
["baz"]
>>> foo()
["baz"]

Common Mistake #2: Using class variables incorrectly

Consider the following example:

>>> class A(object):
...     x = 1
...
>>> class B(A):
...     pass
...
>>> class C(A):
...     pass
...
>>> print A.x, B.x, C.x
1 1 1

Makes sense.

>>> B.x = 2
>>> print A.x, B.x, C.x
1 2 1

Yup, again as expected.

>>> A.x = 3
>>> print A.x, B.x, C.x
3 2 3

What the $%#!&?? We only changed A.x. Why did C.x change too?

In Python, class variables are internally handled as dictionaries and follow what is often referred to as Method Resolution Order (MRO). So in the above code, since the attribute x is not found in class C, it will be looked up in its base classes (only A in the above example, although Python supports multiple inheritances). In other words, C doesn’t have its own x property, independent of A. Thus, references to C.x are in fact references to A.x. This causes a Python problem unless it’s handled properly. Learn more about class attributes in Python.

Common Mistake #3: Specifying parameters incorrectly for an exception block

Suppose you have the following code:

>>> try:
...     l = ["a", "b"]
...     int(l[2])
... except ValueError, IndexError:  # To catch both exceptions, right?
...     pass
...
Traceback (most recent call last):
  File "", line 3, in 
IndexError: list index out of range

The problem here is that the except statement does not take a list of exceptions specified in this manner. Rather, In Python 2.x, the syntax except Exception, e is used to bind the exception to the optional second parameter specified (in this case e), in order to make it available for further inspection. As a result, in the above code, the IndexError exception is not being caught by the except statement; rather, the exception instead ends up being bound to a parameter named IndexError.

The proper way to catch multiple exceptions in an except statement is to specify the first parameter as a tuple containing all exceptions to be caught. Also, for maximum portability, use the as keyword, since that syntax is supported by both Python 2 and Python 3:

>>> try:
...     l = ["a", "b"]
...     int(l[2])
... except (ValueError, IndexError) as e:  
...     pass
...
>>>

Common Mistake #4: Misunderstanding Python scope rules

Python scope resolution is based on what is known as the LEGB rule, which is shorthand for Local, Enclosing, Global, Built-in. Seems straightforward enough, right? Well, actually, there are some subtleties to the way this works in Python, which brings us to the common more advanced Python programming problem below. Consider the following:

>>> x = 10
>>> def foo():
...     x += 1
...     print x
...
>>> foo()
Traceback (most recent call last):
  File "", line 1, in 
  File "", line 2, in foo
UnboundLocalError: local variable 'x' referenced before assignment

What’s the problem?

The above error occurs because, when you make an assignment to a variable in a scope, that variable is automatically considered by Python to be local to that scope and shadows any similarly named variable in any outer scope.

Many are thereby surprised to get an UnboundLocalError in previously working code when it is modified by adding an assignment statement somewhere in the body of a function. (You can read more about this here.)

It is particularly common for this to trip up developers when using lists. Consider the following example:

>>> lst = [1, 2, 3]
>>> def foo1():
...     lst.append(5)   # This works ok...
...
>>> foo1()
>>> lst
[1, 2, 3, 5]

>>> lst = [1, 2, 3]
>>> def foo2():
...     lst += [5]      # ... but this bombs!
...
>>> foo2()
Traceback (most recent call last):
  File "", line 1, in 
  File "", line 2, in foo
UnboundLocalError: local variable 'lst' referenced before assignment

Huh? Why did foo2 bomb while foo1 ran fine?

The answer is the same as in the prior example problem but is admittedly more subtle. foo1 is not making an assignment to lst, whereas foo2 is. Remembering that lst += [5] is really just shorthand for lst = lst + [5], we see that we are attempting to assign a value to lst (therefore presumed by Python to be in the local scope). However, the value we are looking to assign to lstis based on lst itself (again, now presumed to be in the local scope), which has not yet been defined. Boom.

Common Mistake #5: Modifying a list while iterating over it

The problem with the following code should be fairly obvious:

>>> odd = lambda x : bool(x % 2)
>>> numbers = [n for n in range(10)]
>>> for i in range(len(numbers)):
...     if odd(numbers[i]):
...         del numbers[i]  # BAD: Deleting item from a list while iterating over it
...
Traceback (most recent call last):
  	  File "", line 2, in 
IndexError: list index out of range

Deleting an item from a list or array while iterating over it is a Python problem that is well known to any experienced software developer. But while the example above may be fairly obvious, even advanced developers can be unintentionally bitten by this in code that is much more complex.

Fortunately, Python incorporates a number of elegant programming paradigms which, when used properly, can result in significantly simplified and streamlined code. A side benefit of this is that simpler code is less likely to be bitten by the accidental-deletion-of-a-list-item-while-iterating-over-it bug. One such paradigm is that of list comprehensions. Moreover, list comprehensions are particularly useful for avoiding this specific problem, as shown by this alternate implementation of the above code which works perfectly:

>>> odd = lambda x : bool(x % 2)
>>> numbers = [n for n in range(10)]
>>> numbers[:] = [n for n in numbers if not odd(n)]  # ahh, the beauty of it all
>>> numbers
[0, 2, 4, 6, 8]

Common Mistake #6: Confusing how Python binds variables in closures

Considering the following example:

>>> def create_multipliers():
...     return [lambda x : i * x for i in range(5)]
>>> for multiplier in create_multipliers():
...     print multiplier(2)
...

You might expect the following output:

0
2
4
6
8

But you actually get:

8
8
8
8
8

Surprise!

This happens due to Python’s late binding behavior which says that the values of variables used in closures are looked up at the time the inner function is called. So in the above code, whenever any of the returned functions are called, the value of i is looked up in the surrounding scope at the time it is called (and by then, the loop has completed, so i has already been assigned its final value of 4).

The solution to this common Python problem is a bit of a hack:

>>> def create_multipliers():
...     return [lambda x, i=i : i * x for i in range(5)]
...
>>> for multiplier in create_multipliers():
...     print multiplier(2)
...
0
2
4
6
8

Voilà! We are taking advantage of default arguments here to generate anonymous functions in order to achieve the desired behavior. Some would call this elegant. Some would call it subtle. Some hate it. But if you’re a Python developer, it’s important to understand in any case.

Common Mistake #7: Creating circular module dependencies

Let’s say you have two files, a.py and b.py, each of which imports the other, as follows:

In a.py:

import b

def f():
    return b.x
	
print f()

And in b.py:

import a

x = 1

def g():
    print a.f()

First, let’s try importing a.py:

>>> import a
1

Worked just fine. Perhaps that surprises you. After all, we do have a circular import here which presumably should be a problem, shouldn’t it?

The answer is that the mere presence of a circular import is not in and of itself a problem in Python. If a module has already been imported, Python is smart enough not to try to re-import it. However, depending on the point at which each module is attempting to access functions or variables defined in the other, you may indeed run into problems.

So returning to our example, when we imported a.py, it had no problem importing b.py, since b.py does not require anything from a.py to be defined at the time it is imported. The only reference in b.py to a is the call to a.f(). But that call is in g() and nothing in a.py or b.pyinvokes g(). So life is good.

But what happens if we attempt to import b.py (without having previously imported a.py, that is):

>>> import b
Traceback (most recent call last):
  	  File "", line 1, in 
  	  File "b.py", line 1, in 
    import a
  	  File "a.py", line 6, in 
	print f()
  	  File "a.py", line 4, in f
	return b.x
AttributeError: 'module' object has no attribute 'x'

Uh-oh. That’s not good! The problem here is that, in the process of importing b.py, it attempts to import a.py, which in turn calls f(), which attempts to access b.x. But b.x has not yet been defined. Hence the AttributeError exception.

At least one solution to this is quite trivial. Simply modify b.py to import a.py within g():

x = 1

def g():
    import a	# This will be evaluated only when g() is called
    print a.f()

No when we import it, everything is fine:

>>> import b
>>> b.g()
1	# Printed a first time since module 'a' calls 'print f()' at the end
1	# Printed a second time, this one is our call to 'g'

Common Mistake #8: Name clashing with Python Standard Library modules

One of the beauties of Python is the wealth of library modules that it comes with “out of the box”. But as a result, if you’re not consciously avoiding it, it’s not that difficult to run into a name clash between the name of one of your modules and a module with the same name in the standard library that ships with Python (for example, you might have a module named email.py in your code, which would be in conflict with the standard library module of the same name).

This can lead to gnarly problems, such as importing another library which in turns tries to import the Python Standard Library version of a module but, since you have a module with the same name, the other package mistakenly imports your version instead of the one within the Python Standard Library. This is where bad Python errors happen.

Care should, therefore, be exercised to avoid using the same names as those in the Python Standard Library modules. It’s way easier for you to change the name of a module within your package than it is to file a Python Enhancement Proposal (PEP) to request a name change upstream and to try and get that approved.

Common Mistake #9: Failing to address differences between Python 2 and Python 3

Consider the following file foo.py:

import sys

def bar(i):
    if i == 1:
        raise KeyError(1)
    if i == 2:
        raise ValueError(2)

def bad():
    e = None
    try:
        bar(int(sys.argv[1]))
    except KeyError as e:
        print('key error')
    except ValueError as e:
        print('value error')
    print(e)

bad()

On Python 2, this runs fine:

$ python foo.py 1
key error
1
$ python foo.py 2
value error
2

But now let’s give it a whirl on Python 3:

$ python3 foo.py 1
key error
Traceback (most recent call last):
  File "foo.py", line 19, in 
    bad()
  File "foo.py", line 17, in bad
    print(e)
UnboundLocalError: local variable 'e' referenced before assignment

What has just happened here? The “problem” is that, in Python 3, the exception object is not accessible beyond the scope of the except block. (The reason for this is that, otherwise, it would keep a reference cycle with the stack frame in memory until the garbage collector runs and purges the references from memory. More technical detail about this is available here).

One way to avoid this issue is to maintain a reference to the exception object outside the scope of the except block so that it remains accessible. Here’s a version of the previous example that uses this technique, thereby yielding code that is both Python 2 and Python 3 friendly:

import sys

def bar(i):
    if i == 1:
        raise KeyError(1)
    if i == 2:
        raise ValueError(2)

def good():
    exception = None
    try:
        bar(int(sys.argv[1]))
    except KeyError as e:
        exception = e
        print('key error')
    except ValueError as e:
        exception = e
        print('value error')
    print(exception)

good()

Running this on Py3k:

$ python3 foo.py 1
key error
1
$ python3 foo.py 2
value error
2

Yippee!

(Incidentally, our Python Hiring Guide discusses a number of other important differences to be aware of when migrating code from Python 2 to Python 3.)

Common Mistake #10: Misusing the __del__ method

Let’s say you had this in a file called mod.py:

import foo

class Bar(object):
   	    ...
    def __del__(self):
        foo.cleanup(self.myhandle)

And you then tried to do this from another_mod.py:

import mod
mybar = mod.Bar()

You’d get an ugly AttributeError exception.

Why? Because, as reported here, when the interpreter shuts down, the module’s global variables are all set to None. As a result, in the above example, at the point that [__del__](https://docs.python.org/2/reference/datamodel.html#object.__del__ "__del__") is invoked, the name foo has already been set to None.

A solution to this somewhat more advanced Python programming problem would be to use [atexit.register()](https://docs.python.org/2/library/atexit.html "atexit.register()") instead. That way, when your program is finished executing (when exiting normally, that is), your registered handlers are kicked off before the interpreter is shut down.

With that understanding, a fix for the above mod.py code might then look something like this:

import foo
import atexit

def cleanup(handle):
    foo.cleanup(handle)


class Bar(object):
    def __init__(self):
        ...
        atexit.register(cleanup, self.myhandle)

This implementation provides a clean and reliable way of calling any needed cleanup functionality upon normal program termination. Obviously, it’s up to foo.cleanup to decide what to do with the object bound to the name self.myhandle, but you get the idea.

Wrap-up

Python is a powerful and flexible language with many mechanisms and paradigms that can greatly improve productivity. As with any software tool or language, though, having a limited understanding or appreciation of its capabilities can sometimes be more of an impediment than a benefit, leaving one in the proverbial state of “knowing enough to be dangerous”.

Familiarizing oneself with the key nuances of Python, such as (but by no means limited to) the moderately advanced programming problems raised in this article, will help optimize use of the language while avoiding some of its more common errors.

You might also want to check out our Insider’s Guide to Python Interviewing for suggestions on interview questions that can help identify Python experts.

We hope you’ve found the pointers in this article helpful and welcome your feedback.

Angular 8 Pagination Example and Tutorial

Angular 8 Pagination Example and Tutorial

Pagination is the best way to show huge number of records in series for any application. Also showing/fetching thousands of record at one go will affect the performance of the application.

Pagination is the best way to show huge number of records in series for any application. Also showing/fetching thousands of record at one go will affect the performance of the application.

For example, when you search something that returns a large number of records which cannot be shown on a single web page therefore, those records are part into number of pages that can be accessed through links via pagination structure.

So today in this demo we will discuss the simple pagination in Angular 8.

Step 1: Create a basic app with angular cli
ng new angular8-simple-pagination-example

By typing the above command we will see a basic angular app created on the current folder. So move to the created folder by typing **cd angular8-simple-pagination-example/. **You can check the newly created app by typing http://localhost:4200 on the browser.

Step 2: install ngx-pagination pagination dependency from terminal

So run the below command over terminal

npm install ngx-pagination --save

Step 3: Create dummy records for pagination

Now we will create static data to show the pagination. So lets have a look on the code under file **app.component.ts **

import { Component } from '@angular/core';
import {NgxPaginationModule} from 'ngx-pagination';
@Component({
   selector: 'app-root',
   templateUrl: './app.component.html',
   styleUrls: ['./app.component.css']
})
export class AppComponent {
   title = 'simple pagination demo';
   collection = [];
   constructor(){
     for(let i=1;i<=100;i++){
       let Obj = {'name': `Employee Name ${i}`,'code': `EMP00 ${i}`}
       this.collection.push(Obj);
     }
   }
}

In the above file, we can see that inside constructor we have created a loop for created dummy record for 100 employees having employee name & code for showing pagination.

Step 4: Import dependency in app.module.ts

Now let's have a look on the code inside **app.module.ts **where the ngx-pagination module has been imported

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
 
import { NgxPaginationModule } from 'ngx-pagination';
import { AppComponent } from './app.component';
 
@NgModule({
declarations: [
AppComponent
],
imports: [
BrowserModule,
NgxPaginationModule
],
providers: [],
bootstrap: [AppComponent]
})
export class AppModule { }

Step 5: Update view from app.component.html

Now one last step needed to do is, add the below code anywhere inside app.component.html

*  Emp Name | Emp code
 {{item.name}} | {{item.code}} 


Now, we are done with all the needed steps for the pagination in our angular application.

Step 6: Run the app

Run the app over the terminal with npm start and check the app after typing the url http://localhost:4200/.** **A page will open like below:

Conclusion

By following these easy steps we can easily achieve the client side pagination in Angular 8 application. If you want to impliment server side pagination in angular8 Server Side Pagination in Angular Example and Tutorial . You can also find other demos of Angular Sample Application here to start working on enterprise level application. Click here to view more about the pagination package over npm.

Create Simple Login Page using Angular 8 and HTTP Authentication

Create Simple Login Page using Angular 8 and HTTP Authentication

In this article, you'll learn how to setup a simple login page using Angular 8 and Basic HTTP authentication

In this article, you'll learn how to setup a simple login page using Angular 8 and Basic HTTP authentication

Tutorial built with Angular 8.0.2 and the Angular CLI

Angular CLI was used to generate the base project structure with the ng new command, the CLI is also used to build and serve the application. For more info about the Angular CLI see https://angular.io/cli.

Styling of the example app is all done with Bootstrap 4.3, for more info about Bootstrap see https://getbootstrap.com/docs/4.3/getting-started/introduction/.

Running the Angular 8 Basic Authentication Tutorial Example Locally
  1. Install NodeJS and NPM from https://nodejs.org/en/download/.
  2. Download or clone the tutorial project source code from https://github.com/cornflourblue/angular-8-basic-authentication-example
  3. Install all required npm packages by running npm install from the command line in the project root folder (where the package.json is located).
  4. Start the application by running npm start from the
  5. command line in the project root folder, this will build the application
  6. and automatically launch it in the browser on the URL
  7. http://localhost:4200.

NOTE: You can also run the app directly using the Angular CLI command ng serve --open. To do this first install the Angular CLI globally on your system with the command npm install -g @angular/cli.

Running the Tutorial Example with a Real Backend API

The Angular 8 basic authentication example app uses a fake / mock backend by default so it can run in the browser without a real api, to switch to a real backend api you just have to remove or comment out the line below the comment // provider used to create fake backend located in the /src/app/app.module.ts file.

Angular 8 Tutorial Project Structure

The app and code structure of the tutorial mostly follows the best practice recommendations in the official Angular Style Guide, with a few of my own tweaks here and there.

Each feature has it's own folder (home & login), other shared/common code such as services, models, helpers etc are placed in folders prefixed with an underscore _ to easily differentiate them and group them together at the top of the folder structure.

The index.ts files in each folder are barrel files that group the exported modules from a folder together so they can be imported using the folder path instead of the full module path and to enable importing multiple modules in a single import (e.g. import { AuthenticationService, UserService } from '../_services').

Path aliases @app and @environments have been configured in tsconfig.json that map to the /src/app and /src/environments directories. This allows imports to be relative to the app and environments folders by prefixing import paths with aliases instead of having to use long relative paths (e.g. import MyComponent from '../../../MyComponent').

Here are the main project files that contain the application logic, I left out some files that were generated by Angular CLI ng new command that I didn't change.

  • src
  • app
  • _helpers
  • auth.guard.ts
  • basic-auth.interceptor.ts
  • error.interceptor.ts
  • fake-backend.ts
  • index.ts
  • _models
  • user.ts
  • index.ts
  • _services
  • authentication.service.ts
  • user.service.ts
  • index.ts
  • home
  • home.component.html
  • home.component.ts
  • index.ts
  • login
  • login.component.html
  • login.component.ts
  • index.ts
  • app.component.html
  • app.component.ts
  • app.module.ts
  • app.routing.ts
  • environments
  • environment.prod.ts
  • environment.ts
  • index.html
  • main.ts
  • polyfills.ts
  • styles.less
  • package.json
  • tsconfig.json
Auth Guard

Path: /src/app/_helpers/auth.guard.ts

The auth guard is an angular route guard that's used to prevent unauthenticated users from accessing restricted routes, it does this by implementing the CanActivate interface which allows the guard to decide if a route can be activated with the canActivate() method. If the method returns true the route is activated (allowed to proceed), otherwise if the method returns false the route is blocked.

The auth guard uses the authentication service to check if the user is logged in, if they are logged in it returns true from the canActivate() method, otherwise it returns false and redirects the user to the login page.

Angular route guards are attached to routes in the router config, this auth guard is used in app.routing.ts to protect the home page route.

import { Injectable } from '@angular/core';
import { Router, CanActivate, ActivatedRouteSnapshot, RouterStateSnapshot } from '@angular/router';

import { AuthenticationService } from '@app/_services';

@Injectable({ providedIn: 'root' })
export class AuthGuard implements CanActivate {
    constructor(
        private router: Router,
        private authenticationService: AuthenticationService
    ) { }

    canActivate(route: ActivatedRouteSnapshot, state: RouterStateSnapshot) {
        const currentUser = this.authenticationService.currentUserValue;
        if (currentUser) {
            // logged in so return true
            return true;
        }

        // not logged in so redirect to login page with the return url
        this.router.navigate(['/login'], { queryParams: { returnUrl: state.url } });
        return false;
    }
}
Basic Authentication Interceptor

Path: /src/app/_helpers/basic-auth.interceptor.ts

The Basic Authentication Interceptor intercepts http requests from the application to add basic authentication credentials to the Authorization header if the user is logged in.

It's implemented using the HttpInterceptor class included in the HttpClientModule, by extending the HttpInterceptor class you can create a custom interceptor to modify http requests before they get sent to the server.

Http interceptors are added to the request pipeline in the providers section of the _app.module.ts_ file.

import { Injectable } from '@angular/core';
import { HttpRequest, HttpHandler, HttpEvent, HttpInterceptor } from '@angular/common/http';
import { Observable } from 'rxjs';

import { AuthenticationService } from '@app/_services';

@Injectable()
export class BasicAuthInterceptor implements HttpInterceptor {
    constructor(private authenticationService: AuthenticationService) { }

    intercept(request: HttpRequest, next: HttpHandler): Observable> {
        // add authorization header with basic auth credentials if available
        const currentUser = this.authenticationService.currentUserValue;
        if (currentUser && currentUser.authdata) {
            request = request.clone({
                setHeaders: { 
                    Authorization: `Basic ${currentUser.authdata}`
                }
            });
        }

        return next.handle(request);
    }
}
Http Error Interceptor

Path: /src/app/_helpers/error.interceptor.ts

The Error Interceptor intercepts http responses from the api to check if there were any errors. If there is a 401 Unauthorized response the user is automatically logged out of the application, all other errors are re-thrown up to the calling service so an alert with the error can be displayed on the screen.

It's implemented using the HttpInterceptor class included in the HttpClientModule, by extending the HttpInterceptor class you can create a custom interceptor to catch all error responses from the server in a single location.

Http interceptors are added to the request pipeline in the providers section of the app.module.ts file.

import { Injectable } from '@angular/core';
import { HttpRequest, HttpHandler, HttpEvent, HttpInterceptor } from '@angular/common/http';
import { Observable, throwError } from 'rxjs';
import { catchError } from 'rxjs/operators';

import { AuthenticationService } from '@app/_services';

@Injectable()
export class ErrorInterceptor implements HttpInterceptor {
    constructor(private authenticationService: AuthenticationService) { }

    intercept(request: HttpRequest, next: HttpHandler): Observable> {
        return next.handle(request).pipe(catchError(err => {
            if (err.status === 401) {
                // auto logout if 401 response returned from api
                this.authenticationService.logout();
                location.reload(true);
            }

            const error = err.error.message || err.statusText;
            return throwError(error);
        }))
    }
}
Fake Backend Provider

Path: /src/app/_helpers/fake-backend.ts

In order to run and test the Angular application without a real backend API, the example uses a fake backend that intercepts the HTTP requests from the Angular app and send back "fake" responses. This is done by a class that implements the Angular HttpInterceptor interface, for more information on Angular HTTP Interceptors see https://angular.io/api/common/http/HttpInterceptor

The fake backend contains a handleRoute function that checks if the request matches one of the faked routes in the switch statement, at the moment this includes POST requests to the /users/authenticate route for handling authentication, and GET requests to the /users route for getting all users.

Requests to the authenticate route are handled by the authenticate() function which checks the username and password against an array of hardcoded users. If the username and password are correct then an ok response is returned with the user details, otherwise an error response is returned.

Requests to the get users route are handled by the getUsers() function which checks if the user is logged in by calling the new isLoggedIn() helper function. If the user is logged in an ok() response with the whole users array is returned, otherwise a 401 Unauthorized response is returned by calling the new unauthorized() helper function.

If the request doesn't match any of the faked routes it is passed through as a real HTTP request to the backend API.

import { Injectable } from '@angular/core';
import { HttpRequest, HttpResponse, HttpHandler, HttpEvent, HttpInterceptor, HTTP_INTERCEPTORS } from '@angular/common/http';
import { Observable, of, throwError } from 'rxjs';
import { delay, mergeMap, materialize, dematerialize } from 'rxjs/operators';

import { User } from '@app/_models';

const users: User[] = [{ id: 1, username: 'test', password: 'test', firstName: 'Test', lastName: 'User' }];

@Injectable()
export class FakeBackendInterceptor implements HttpInterceptor {
    intercept(request: HttpRequest, next: HttpHandler): Observable> {
        const { url, method, headers, body } = request;

        // wrap in delayed observable to simulate server api call
        return of(null)
            .pipe(mergeMap(handleRoute))
            .pipe(materialize()) // call materialize and dematerialize to ensure delay even if an error is thrown (https://github.com/Reactive-Extensions/RxJS/issues/648)
            .pipe(delay(500))
            .pipe(dematerialize());

        function handleRoute() {
            switch (true) {
                case url.endsWith('/users/authenticate') && method === 'POST':
                    return authenticate();
                case url.endsWith('/users') && method === 'GET':
                    return getUsers();
                default:
                    // pass through any requests not handled above
                    return next.handle(request);
            }    
        }

        // route functions

        function authenticate() {
            const { username, password } = body;
            const user = users.find(x => x.username === username && x.password === password);
            if (!user) return error('Username or password is incorrect');
            return ok({
                id: user.id,
                username: user.username,
                firstName: user.firstName,
                lastName: user.lastName
            })
        }

        function getUsers() {
            if (!isLoggedIn()) return unauthorized();
            return ok(users);
        }

        // helper functions

        function ok(body?) {
            return of(new HttpResponse({ status: 200, body }))
        }

        function error(message) {
            return throwError({ error: { message } });
        }

        function unauthorized() {
            return throwError({ status: 401, error: { message: 'Unauthorised' } });
        }

        function isLoggedIn() {
            return headers.get('Authorization') === `Basic ${window.btoa('test:test')}`;
        }
    }
}

export let fakeBackendProvider = {
    // use fake backend in place of Http service for backend-less development
    provide: HTTP_INTERCEPTORS,
    useClass: FakeBackendInterceptor,
    multi: true
};
User Model

Path: /src/app/_models/user.ts

The user model is a small class that defines the properties of a user.

export class User {
    id: number;
    username: string;
    password: string;
    firstName: string;
    lastName: string;
    authdata?: string;
}
Authentication Service

Path: /src/app/_services/authentication.service.ts

The authentication service is used to login & logout of the Angular app, it notifies other components when the user logs in & out, and allows access the currently logged in user.

RxJS Subjects and Observables are used to store the current user object and notify other components when the user logs in and out of the app. Angular components can subscribe() to the public currentUser: Observable property to be notified of changes, and notifications are sent when the this.currentUserSubject.next() method is called in the login() and logout() methods, passing the argument to each subscriber. The RxJS BehaviorSubject is a special type of Subject that keeps hold of the current value and emits it to any new subscribers as soon as they subscribe, while regular Subjects don't store the current value and only emit values that are published after a subscription is created.

The login() method sends the user credentials to the API via an HTTP POST request for authentication. If successful the user's basic authentication data (base64 encoded username and password) is added to the user object and stored in localStorage to keep the user logged in between page refreshes. The user object is then published to all subscribers with the call to this.currentUserSubject.next(user);.

The basic auth data is used by the basic authentication interceptor above to set the authorization header of http requests made to secure api endpoints.

The constructor() of the service initialises the currentUserSubject with the currentUser object from localStorage which enables the user to stay logged in between page refreshes or after the browser is closed. The public currentUser property is then set to this.currentUserSubject.asObservable(); which allows other components to subscribe to the currentUser Observable but doesn't allow them to publish to the currentUserSubject, this is so logging in and out of the app can only be done via the authentication service.

The currentUserValue getter allows other components an easy way to get the value of the currently logged in user without having to subscribe to the currentUser Observable.

The logout() method removes the current user object from local storage and publishes null to the currentUserSubject to notify all subscribers that the user has logged out.

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { BehaviorSubject, Observable } from 'rxjs';
import { map } from 'rxjs/operators';

import { environment } from '@environments/environment';
import { User } from '@app/_models';

@Injectable({ providedIn: 'root' })
export class AuthenticationService {
    private currentUserSubject: BehaviorSubject;
    public currentUser: Observable;

    constructor(private http: HttpClient) {
        this.currentUserSubject = new BehaviorSubject(JSON.parse(localStorage.getItem('currentUser')));
        this.currentUser = this.currentUserSubject.asObservable();
    }

    public get currentUserValue(): User {
        return this.currentUserSubject.value;
    }

    login(username: string, password: string) {
        return this.http.post(`${environment.apiUrl}/users/authenticate`, { username, password })
            .pipe(map(user => {
                // store user details and basic auth credentials in local storage to keep user logged in between page refreshes
                user.authdata = window.btoa(username + ':' + password);
                localStorage.setItem('currentUser', JSON.stringify(user));
                this.currentUserSubject.next(user);
                return user;
            }));
    }

    logout() {
        // remove user from local storage to log user out
        localStorage.removeItem('currentUser');
        this.currentUserSubject.next(null);
    }
}
User Service

Path: /src/app/_services/user.service.ts

The user service contains a method for getting all users from the api, I included it to demonstrate accessing a secure api endpoint with the http authorization header set after logging in to the application, the auth header is automatically set with basic authentication credentials by the basic authentication interceptor. The secure endpoint in the example is a fake one implemented in the fake backend provider.

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';

import { environment } from '@environments/environment';
import { User } from '@app/_models';

@Injectable({ providedIn: 'root' })
export class UserService {
    constructor(private http: HttpClient) { }

    getAll() {
        return this.http.get(`${environment.apiUrl}/users`);
    }
}
Home Component Template

Path: /src/app/home/home.component.html

The home component template contains html and angular 8 template syntax for displaying a simple welcome message and a list of users from a secure api endpoint.


    #### You're logged in with Angular 8 & Basic HTTP Authentication!!

    
        ###### Users from secure api end point

        

        
            {{user.firstName}} {{user.lastName}}
        
    

Home Component

Path: /src/app/home/home.component.ts

The home component defines an angular 8 component that gets all users from the user service and makes them available to the template via a users array property.

import { Component } from '@angular/core';
import { first } from 'rxjs/operators';

import { User } from '@app/_models';
import { UserService } from '@app/_services';

@Component({ templateUrl: 'home.component.html' })
export class HomeComponent {
    loading = false;
    users: User[];

    constructor(private userService: UserService) { }

    ngOnInit() {
        this.loading = true;
        this.userService.getAll().pipe(first()).subscribe(users => {
            this.loading = false;
            this.users = users;
        });
    }
}
Login Component Template

Path: /src/app/login/login.component.html

The login component template contains a login form with username and password fields. It displays validation messages for invalid fields when the submit button is clicked. The form submit event is bound to the onSubmit() method of the login component.


    
        Username: test

        Password: test
    
    
        #### Angular 8 Basic Auth Login Example

        
            
                
                    Username
                    
                    
                        Username is required

                    
                
                
                    Password
                    
                    
                        Password is required

                    
                
                
                    
                    Login
                
                {{error}}

            
        
    

Login Component

Path: /src/app/login/login.component.ts

The login component uses the authentication service to login to the application. If the user is already logged in they are automatically redirected to the home page.

The loginForm: FormGroup object defines the form controls and validators, and is used to access data entered into the form. The FormGroup is part of the Angular Reactive Forms module and is bound to the login template above with the [formGroup]="loginForm" directive.

import { Component, OnInit } from '@angular/core';
import { Router, ActivatedRoute } from '@angular/router';
import { FormBuilder, FormGroup, Validators } from '@angular/forms';
import { first } from 'rxjs/operators';

import { AuthenticationService } from '@app/_services';

@Component({ templateUrl: 'login.component.html' })
export class LoginComponent implements OnInit {
    loginForm: FormGroup;
    loading = false;
    submitted = false;
    returnUrl: string;
    error = '';

    constructor(
        private formBuilder: FormBuilder,
        private route: ActivatedRoute,
        private router: Router,
        private authenticationService: AuthenticationService
    ) { 
        // redirect to home if already logged in
        if (this.authenticationService.currentUserValue) { 
            this.router.navigate(['/']);
        }
    }

    ngOnInit() {
        this.loginForm = this.formBuilder.group({
            username: ['', Validators.required],
            password: ['', Validators.required]
        });

        // get return url from route parameters or default to '/'
        this.returnUrl = this.route.snapshot.queryParams['returnUrl'] || '/';
    }

    // convenience getter for easy access to form fields
    get f() { return this.loginForm.controls; }

    onSubmit() {
        this.submitted = true;

        // stop here if form is invalid
        if (this.loginForm.invalid) {
            return;
        }

        this.loading = true;
        this.authenticationService.login(this.f.username.value, this.f.password.value)
            .pipe(first())
            .subscribe(
                data => {
                    this.router.navigate([this.returnUrl]);
                },
                error => {
                    this.error = error;
                    this.loading = false;
                });
    }
}
App Component Template

Path: /src/app/app.component.html

The app component template is the root component template of the application, it contains the main nav bar which is only displayed for authenticated users, and a router-outlet directive for displaying the contents of each view based on the current route / path.



    
        Home
        Logout
    




    

App Component

Path: /src/app/app.component.ts

The app component is the root component of the application, it defines the root tag of the app as `` with the selector property of the @Component() decorator.

It subscribes to the currentUser observable in the authentication service so it can reactively show/hide the main navigation bar when the user logs in/out of the application. I didn't worry about unsubscribing from the observable here because it's the root component of the application, the only time the component will be destroyed is when the application is closed which would destroy any subscriptions as well.

The app component contains a logout() method which is called from the logout link in the main nav bar above to log the user out and redirect them to the login page.

import { Component } from '@angular/core';
import { Router } from '@angular/router';

import { AuthenticationService } from './_services';
import { User } from './_models';

@Component({ selector: 'app', templateUrl: 'app.component.html' })
export class AppComponent {
    currentUser: User;

    constructor(
        private router: Router,
        private authenticationService: AuthenticationService
    ) {
        this.authenticationService.currentUser.subscribe(x => this.currentUser = x);
    }

    logout() {
        this.authenticationService.logout();
        this.router.navigate(['/login']);
    }
}
App Module

Path: /src/app/app.module.ts

The app module defines the root module of the application along with metadata about the module. For more info about angular 8 modules check out this page on the official docs site.

This is where the fake backend provider is added to the application, to switch to a real backend simply remove the providers located below the comment // provider used to create fake backend.

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { ReactiveFormsModule } from '@angular/forms';
import { HttpClientModule, HTTP_INTERCEPTORS } from '@angular/common/http';

// used to create fake backend
import { fakeBackendProvider } from './_helpers';

import { AppComponent } from './app.component';
import { appRoutingModule } from './app.routing';

import { BasicAuthInterceptor, ErrorInterceptor } from './_helpers';
import { HomeComponent } from './home';
import { LoginComponent } from './login';

@NgModule({
    imports: [
        BrowserModule,
        ReactiveFormsModule,
        HttpClientModule,
        appRoutingModule
    ],
    declarations: [
        AppComponent,
        HomeComponent,
        LoginComponent
    ],
    providers: [
        { provide: HTTP_INTERCEPTORS, useClass: BasicAuthInterceptor, multi: true },
        { provide: HTTP_INTERCEPTORS, useClass: ErrorInterceptor, multi: true },

        // provider used to create fake backend
        fakeBackendProvider
    ],
    bootstrap: [AppComponent]
})
export class AppModule { }
App Routing Module

Path: /src/app/app.routing.ts

Routing for the Angular app is configured as an array of Routes, each component is mapped to a path so the Angular Router knows which component to display based on the URL in the browser address bar. The home route is secured by passing the AuthGuard to the canActivate property of the route.

The Routes array is passed to the RouterModule.forRoot() method which creates a routing module with all of the app routes configured, and also includes all of the Angular Router providers and directives such as the `` directive. For more information on Angular Routing and Navigation see https://angular.io/guide/router.

import { Routes, RouterModule } from '@angular/router';

import { HomeComponent } from './home';
import { LoginComponent } from './login';
import { AuthGuard } from './_helpers';

const routes: Routes = [
    { path: '', component: HomeComponent, canActivate: [AuthGuard] },
    { path: 'login', component: LoginComponent },

    // otherwise redirect to home
    { path: '**', redirectTo: '' }
];

export const appRoutingModule = RouterModule.forRoot(routes);
Production Environment Config

Path: /src/environments/environment.prod.ts

The production environment config contains variables required to run the application in production. This enables you to build the application with a different configuration for each different environment (e.g. production & development) without updating the app code.

When you build the application for production with the command ng build --prod, the output environment.ts is replaced with environment.prod.ts.

export const environment = {
    production: true,
    apiUrl: 'http://localhost:4000'
};
Development Environment Config

Path: /src/environments/environment.ts

The development environment config contains variables required to run the application in development.

Environment config is accessed by importing the environment object into any Angular service of component with the line import { environment } from '@environments/environment' and accessing properties on the environment object, see the user service for an example.

export const environment = {
    production: false,
    apiUrl: 'http://localhost:4000'
};
Main Index Html File

Path: /src/index.html

The main index.html file is the initial page loaded by the browser that kicks everything off. The Angular CLI (with Webpack under the hood) bundles all of the compiled javascript files together and injects them into the body of the index.html page so the scripts can be loaded and executed by the browser.




    
    Angular 8 - Basic HTTP Authentication Tutorial & Example
    

    
    


    Loading...


Main (Bootstrap) File

Path: /src/main.ts

The main file is the entry point used by angular to launch and bootstrap the application.

import { enableProdMode } from '@angular/core';
import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';

import { AppModule } from './app/app.module';
import { environment } from './environments/environment';

if (environment.production) {
    enableProdMode();
}

platformBrowserDynamic().bootstrapModule(AppModule)
    .catch(err => console.error(err));
Polyfills

Path: /src/polyfills.ts

Some features used by Angular 8 are not yet supported natively by all major browsers, polyfills are used to add support for features where necessary so your Angular 8 application works across all major browsers.

This file is generated by the Angular CLI when creating a new project with the ng new command, I've excluded the comments in the file for brevity.

import 'zone.js/dist/zone';
Global LESS/CSS Styles

Path: /src/styles.less

The global styles file contains LESS/CSS styles that are applied globally throughout the application.

/* You can add global styles to this file, and also import other style files */
a { cursor: pointer }
npm package.json

Path: /package.json

The package.json file contains project configuration information including package dependencies which get installed when you run npm install. Full documentation is available on the npm docs website.

{
    "name": "angular-8-basic-authentication-example",
    "version": "1.0.0",
    "scripts": {
        "ng": "ng",
        "start": "ng serve --open",
        "build": "ng build",
        "test": "ng test",
        "lint": "ng lint",
        "e2e": "ng e2e"
    },
    "private": true,
    "dependencies": {
        "@angular/animations": "~8.0.1",
        "@angular/common": "~8.0.1",
        "@angular/compiler": "~8.0.1",
        "@angular/core": "~8.0.1",
        "@angular/forms": "~8.0.1",
        "@angular/platform-browser": "~8.0.1",
        "@angular/platform-browser-dynamic": "~8.0.1",
        "@angular/router": "~8.0.1",
        "rxjs": "~6.4.0",
        "tslib": "^1.9.0",
        "zone.js": "~0.9.1"
    },
    "devDependencies": {
        "@angular-devkit/build-angular": "~0.800.0",
        "@angular/cli": "~8.0.3",
        "@angular/compiler-cli": "~8.0.1",
        "@angular/language-service": "~8.0.1",
        "@types/node": "~8.9.4",
        "@types/jasmine": "~3.3.8",
        "@types/jasminewd2": "~2.0.3",
        "codelyzer": "^5.0.0",
        "jasmine-core": "~3.4.0",
        "jasmine-spec-reporter": "~4.2.1",
        "karma": "~4.1.0",
        "karma-chrome-launcher": "~2.2.0",
        "karma-coverage-istanbul-reporter": "~2.0.1",
        "karma-jasmine": "~2.0.1",
        "karma-jasmine-html-reporter": "^1.4.0",
        "protractor": "~5.4.0",
        "ts-node": "~7.0.0",
        "tslint": "~5.15.0",
        "typescript": "~3.4.3"
    }
}
TypeScript tsconfig.json

Path: /tsconfig.json

The tsconfig.json file configures how the TypeScript compiler will convert TypeScript into JavaScript that is understood by the browser. More information is available on the TypeScript docs.

Most of the file is unchanged from when it was generated by the Angular CLI, only the paths property has been added to map @app and @environments to the /src/app and /src/environments directories. This allows imports to be relative to the app and environments folders by prefixing import paths with aliases instead of having to use long relative paths (e.g. import MyComponent from '../../../MyComponent').

{
    "compileOnSave": false,
    "compilerOptions": {
        "baseUrl": "./",
        "outDir": "./dist/out-tsc",
        "sourceMap": true,
        "declaration": false,
        "downlevelIteration": true,
        "emitDecoratorMetadata": true,
        "experimentalDecorators": true,
        "module": "esnext",
        "moduleResolution": "node",
        "importHelpers": true,
        "target": "es2015",
        "typeRoots": [
            "node_modules/@types"
        ],
        "lib": [
            "es2018",
            "dom"
        ],
        "paths": {
            "@app/*": ["src/app/*"],
            "@environments/*": ["src/environments/*"]
        }
    }
}

The tutorial code is available on GitHub

Laravel 5.8 Tutorial - How to build user roles and permissions on Laravel 5.8 App

Laravel 5.8 Tutorial - How to build user roles and permissions on Laravel 5.8 App

In this article, you'll learn how to user build roles and permissions on Laravel 5.8 Application. You can do it acl in Laravel 5.8 using spatie composer package. I will explain how to implement User Roles and Permissions(ACL) using spatie/laravel-permission composer package.

In this article, you'll learn how to user build roles and permissions on Laravel 5.8 Application. You can do it acl in Laravel 5.8 using spatie composer package. I will explain how to implement User Roles and Permissions(ACL) using spatie/laravel-permission composer package.

Spatie role permission composer package provide way to create acl in Laravel 5.8. They provide how to assign role to user, how to assign permission to user and how to assign permission assign to roles. I will write step by step creating roles and permissions in Laravel 5.8 application.

Roles and Permissions through you can create several types of users with different role and permission, i mean some user have only see listing of items module, some user can also edit items modules, for delete and etc.

In this examples i created three modules as listed bellow:

  • User Management
  • Role Management
  • Product Management

After register user, you don't have any roles, so you can edit your details and assign admin role to you from User Management. After that you can create your own role with permission like role-list, role-create, role-edit, role-delete, product-list, product-create, product-edit, product-delete. You can check with assign new user and check that.

Step 1: Laravel 5.8 Installation

We are going from scratch so, If you haven't installed Laravel in your system then you can run bellow command and get fresh Laravel project.

composer create-project --prefer-dist laravel/laravel blog

Step 2: Install Composer Packages

Now we require to install Spatie package for ACL, that way we can use it's method. Also we will install form collection package. So Open your terminal and run bellow command.

composer require spatie/laravel-permission
  
composer require laravelcollective/html

Now open config/app.php file and add service provider and aliase.

config/app.php

'providers' => [
	....
	Spatie\Permission\PermissionServiceProvider::class,
	Collective\Html\HtmlServiceProvider::class,
],
'aliases' => [
	....
	'Form' => Collective\Html\FormFacade::class,
	'Html' => Collective\Html\HtmlFacade::class,
],

We can also custom changes on Spatie package, so if you also want to changes then you can fire bellow command and get config file in config/permission.php.

php artisan vendor:publish --provider="Spatie\Permission\PermissionServiceProvider" --tag="config"

Step 3: Create Migrations

In this step we have to create three migrations for as listed bellow tables:

  1. users

  2. products

  3. roles

  4. permissions

  5. model_has_permissions

  6. model_has_roles

  7. role_has_permissions

So, if you install fresh project then you have already users table migration but if you don't have products table, so can create manually and other table can create using Spatie package command, so run bellow command and check migration file also.

php artisan vendor:publish --provider="Spatie\Permission\PermissionServiceProvider" --tag="migrations"
php artisan make:migration create_products_table

users table:

<?php

use Illuminate\Support\Facades\Schema;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class CreateUsersTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('users', function (Blueprint $table) {
            $table->bigIncrements('id');
            $table->string('name');
            $table->string('email');
            $table->string('password');
            $table->rememberToken();
            $table->timestamps();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('users');
    }
}

products table:

<?php

use Illuminate\Support\Facades\Schema;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class CreateProductsTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('products', function (Blueprint $table) {
            $table->bigIncrements('id');
            $table->string('name');
            $table->text('detail');
            $table->timestamps();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('products');
    }
}

Spatie tables:

<?php

use Illuminate\Support\Facades\Schema;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class CreatePermissionTables extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        $tableNames = config('permission.table_names');

        Schema::create($tableNames['permissions'], function (Blueprint $table) {
            $table->increments('id');
            $table->string('name');
            $table->string('guard_name');
            $table->timestamps();
        });

        Schema::create($tableNames['roles'], function (Blueprint $table) {
            $table->increments('id');
            $table->string('name');
            $table->string('guard_name');
            $table->timestamps();
        });

        Schema::create($tableNames['model_has_permissions'], function (Blueprint $table) use ($tableNames) {
            $table->integer('permission_id')->unsigned();
            $table->morphs('model');

            $table->foreign('permission_id')
                ->references('id')
                ->on($tableNames['permissions'])
                ->onDelete('cascade');

            $table->primary(['permission_id', 'model_id', 'model_type']);
        });

        Schema::create($tableNames['model_has_roles'], function (Blueprint $table) use ($tableNames) {
            $table->integer('role_id')->unsigned();
            $table->morphs('model');

            $table->foreign('role_id')
                ->references('id')
                ->on($tableNames['roles'])
                ->onDelete('cascade');

            $table->primary(['role_id', 'model_id', 'model_type']);
        });

        Schema::create($tableNames['role_has_permissions'], function (Blueprint $table) use ($tableNames) {
            $table->integer('permission_id')->unsigned();
            $table->integer('role_id')->unsigned();

            $table->foreign('permission_id')
                ->references('id')
                ->on($tableNames['permissions'])
                ->onDelete('cascade');

            $table->foreign('role_id')
                ->references('id')
                ->on($tableNames['roles'])
                ->onDelete('cascade');

            $table->primary(['permission_id', 'role_id']);

            app('cache')->forget('spatie.permission.cache');
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        $tableNames = config('permission.table_names');

        Schema::drop($tableNames['role_has_permissions']);
        Schema::drop($tableNames['model_has_roles']);
        Schema::drop($tableNames['model_has_permissions']);
        Schema::drop($tableNames['roles']);
        Schema::drop($tableNames['permissions']);
    }
}

Now run migration:

php artisan migrate

Step 4: Create Models

In this step we have to create model for User and Product table, so if you get fresh project then you have User Model have so just replace code and other you should create.

app/User.php

<?php
  
namespace App;
  
use Illuminate\Notifications\Notifiable;
use Illuminate\Contracts\Auth\MustVerifyEmail;
use Illuminate\Foundation\Auth\User as Authenticatable;
use Spatie\Permission\Traits\HasRoles;
  
class User extends Authenticatable
{
    use Notifiable;
    use HasRoles;
  
    /**
     * The attributes that are mass assignable.
     *
     * @var array
     */
    protected $fillable = [
        'name', 'email', 'password',
    ];
  
    /**
     * The attributes that should be hidden for arrays.
     *
     * @var array
     */
    protected $hidden = [
        'password', 'remember_token',
    ];
  
    /**
     * The attributes that should be cast to native types.
     *
     * @var array
     */
    protected $casts = [
        'email_verified_at' => 'datetime',
    ];
}

app/Product.php

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Product extends Model
{
    /**
     * The attributes that are mass assignable.
     *	
     * @var array
     */
    protected $fillable = [
        'name', 'detail'
    ];
}

Step 5: Add Middleware

Spatie package provide it's in-built middleware that way we can use it simply and that is display as bellow:

role

permission

So, we have to add middleware in Kernel.php file this way :

app/Http/Kernel.php

....
protected $routeMiddleware = [
	....
	'role' => \Spatie\Permission\Middlewares\RoleMiddleware::class,
	'permission' => \Spatie\Permission\Middlewares\PermissionMiddleware::class,
]
....

Step 6: Create Authentication

In this step we require to create authentication of Laravel 5.8, so laravel provide artisan command to create authentication that way we don't require to create route and controller for login and registration. so run bellow command:

php artisan make:auth

Step 7: Create Routes

We require to add number of route for users module, products module and roles module. In this this route i also use middleware with permission for roles and products route, so add route this way:

routes/web.php

Auth::routes();

Route::get('/home', '[email protected]')->name('home');

Route::group(['middleware' => ['auth']], function() {
    Route::resource('roles','RoleController');
    Route::resource('users','UserController');
    Route::resource('products','ProductController');
});

Step 8: Add Controllers

In this step we have add three controller for users module, products module and roles module so you can create three controller like as bellow:

app/Http/Controllers/UserController.php

<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;
use App\Http\Controllers\Controller;
use App\User;
use Spatie\Permission\Models\Role;
use DB;
use Hash;

class UserController extends Controller
{
    /**
     * Display a listing of the resource.
     *
     * @return \Illuminate\Http\Response
     */
    public function index(Request $request)
    {
        $data = User::orderBy('id','DESC')->paginate(5);
        return view('users.index',compact('data'))
            ->with('i', ($request->input('page', 1) - 1) * 5);
    }

    /**
     * Show the form for creating a new resource.
     *
     * @return \Illuminate\Http\Response
     */
    public function create()
    {
        $roles = Role::pluck('name','name')->all();
        return view('users.create',compact('roles'));
    }

    /**
     * Store a newly created resource in storage.
     *
     * @param  \Illuminate\Http\Request  $request
     * @return \Illuminate\Http\Response
     */
    public function store(Request $request)
    {
        $this->validate($request, [
            'name' => 'required',
            'email' => 'required|email|unique:users,email',
            'password' => 'required|same:confirm-password',
            'roles' => 'required'
        ]);

        $input = $request->all();
        $input['password'] = Hash::make($input['password']);

        $user = User::create($input);
        $user->assignRole($request->input('roles'));

        return redirect()->route('users.index')
                        ->with('success','User created successfully');
    }

    /**
     * Display the specified resource.
     *
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function show($id)
    {
        $user = User::find($id);
        return view('users.show',compact('user'));
    }

    /**
     * Show the form for editing the specified resource.
     *
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function edit($id)
    {
        $user = User::find($id);
        $roles = Role::pluck('name','name')->all();
        $userRole = $user->roles->pluck('name','name')->all();

        return view('users.edit',compact('user','roles','userRole'));
    }

    /**
     * Update the specified resource in storage.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function update(Request $request, $id)
    {
        $this->validate($request, [
            'name' => 'required',
            'email' => 'required|email|unique:users,email,'.$id,
            'password' => 'same:confirm-password',
            'roles' => 'required'
        ]);

        $input = $request->all();
        if(!empty($input['password'])){ 
            $input['password'] = Hash::make($input['password']);
        }else{
            $input = array_except($input,array('password'));    
        }

        $user = User::find($id);
        $user->update($input);
        DB::table('model_has_roles')->where('model_id',$id)->delete();

        $user->assignRole($request->input('roles'));

        return redirect()->route('users.index')
                        ->with('success','User updated successfully');
    }

    /**
     * Remove the specified resource from storage.
     *
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function destroy($id)
    {
        User::find($id)->delete();
        return redirect()->route('users.index')
                        ->with('success','User deleted successfully');
    }
}

app/Http/Controllers/ProductController.php

<?php

namespace App\Http\Controllers;

use App\Product;
use Illuminate\Http\Request;

class ProductController extends Controller
{ 
    /**
     * Display a listing of the resource.
     *
     * @return \Illuminate\Http\Response
     */
    function __construct()
    {
         $this->middleware('permission:product-list|product-create|product-edit|product-delete', ['only' => ['index','show']]);
         $this->middleware('permission:product-create', ['only' => ['create','store']]);
         $this->middleware('permission:product-edit', ['only' => ['edit','update']]);
         $this->middleware('permission:product-delete', ['only' => ['destroy']]);
    }
    /**
     * Display a listing of the resource.
     *
     * @return \Illuminate\Http\Response
     */
    public function index()
    {
        $products = Product::latest()->paginate(5);
        return view('products.index',compact('products'))
            ->with('i', (request()->input('page', 1) - 1) * 5);
    }

    /**
     * Show the form for creating a new resource.
     *
     * @return \Illuminate\Http\Response
     */
    public function create()
    {
        return view('products.create');
    }

    /**
     * Store a newly created resource in storage.
     *
     * @param  \Illuminate\Http\Request  $request
     * @return \Illuminate\Http\Response
     */
    public function store(Request $request)
    {
        request()->validate([
            'name' => 'required',
            'detail' => 'required',
        ]);

        Product::create($request->all());

        return redirect()->route('products.index')
                        ->with('success','Product created successfully.');
    }

    /**
     * Display the specified resource.
     *
     * @param  \App\Product  $product
     * @return \Illuminate\Http\Response
     */
    public function show(Product $product)
    {
        return view('products.show',compact('product'));
    }

    /**
     * Show the form for editing the specified resource.
     *
     * @param  \App\Product  $product
     * @return \Illuminate\Http\Response
     */
    public function edit(Product $product)
    {
        return view('products.edit',compact('product'));
    }

    /**
     * Update the specified resource in storage.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  \App\Product  $product
     * @return \Illuminate\Http\Response
     */
    public function update(Request $request, Product $product)
    {
         request()->validate([
            'name' => 'required',
            'detail' => 'required',
        ]);

        $product->update($request->all());

        return redirect()->route('products.index')
                        ->with('success','Product updated successfully');
    }

    /**
     * Remove the specified resource from storage.
     *
     * @param  \App\Product  $product
     * @return \Illuminate\Http\Response
     */
    public function destroy(Product $product)
    {
        $product->delete();

        return redirect()->route('products.index')
                        ->with('success','Product deleted successfully');
    }
}

app/Http/Controllers/RoleController.php

<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;
use App\Http\Controllers\Controller;
use Spatie\Permission\Models\Role;
use Spatie\Permission\Models\Permission;
use DB;

class RoleController extends Controller
{
    /**
     * Display a listing of the resource.
     *
     * @return \Illuminate\Http\Response
     */
    function __construct()
    {
         $this->middleware('permission:role-list|role-create|role-edit|role-delete', ['only' => ['index','store']]);
         $this->middleware('permission:role-create', ['only' => ['create','store']]);
         $this->middleware('permission:role-edit', ['only' => ['edit','update']]);
         $this->middleware('permission:role-delete', ['only' => ['destroy']]);
    }

    /**
     * Display a listing of the resource.
     *
     * @return \Illuminate\Http\Response
     */
    public function index(Request $request)
    {
        $roles = Role::orderBy('id','DESC')->paginate(5);
        return view('roles.index',compact('roles'))
            ->with('i', ($request->input('page', 1) - 1) * 5);
    }

    /**
     * Show the form for creating a new resource.
     *
     * @return \Illuminate\Http\Response
     */
    public function create()
    {
        $permission = Permission::get();
        return view('roles.create',compact('permission'));
    }

    /**
     * Store a newly created resource in storage.
     *
     * @param  \Illuminate\Http\Request  $request
     * @return \Illuminate\Http\Response
     */
    public function store(Request $request)
    {
        $this->validate($request, [
            'name' => 'required|unique:roles,name',
            'permission' => 'required',
        ]);

        $role = Role::create(['name' => $request->input('name')]);
        $role->syncPermissions($request->input('permission'));

        return redirect()->route('roles.index')
                        ->with('success','Role created successfully');
    }
    /**
     * Display the specified resource.
     *
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function show($id)
    {
        $role = Role::find($id);
        $rolePermissions = Permission::join("role_has_permissions","role_has_permissions.permission_id","=","permissions.id")
            ->where("role_has_permissions.role_id",$id)
            ->get();

        return view('roles.show',compact('role','rolePermissions'));
    }

    /**
     * Show the form for editing the specified resource.
     *
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function edit($id)
    {
        $role = Role::find($id);
        $permission = Permission::get();
        $rolePermissions = DB::table("role_has_permissions")->where("role_has_permissions.role_id",$id)
            ->pluck('role_has_permissions.permission_id','role_has_permissions.permission_id')
            ->all();

        return view('roles.edit',compact('role','permission','rolePermissions'));
    }

    /**
     * Update the specified resource in storage.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function update(Request $request, $id)
    {
        $this->validate($request, [
            'name' => 'required',
            'permission' => 'required',
        ]);

        $role = Role::find($id);
        $role->name = $request->input('name');
        $role->save();

        $role->syncPermissions($request->input('permission'));

        return redirect()->route('roles.index')
                        ->with('success','Role updated successfully');
    }
    /**
     * Remove the specified resource from storage.
     *
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function destroy($id)
    {
        DB::table("roles")->where('id',$id)->delete();
        return redirect()->route('roles.index')
                        ->with('success','Role deleted successfully');
    }
}

Step 9: Add Blade Files

This is last step we have to add numbers view for layouts, users module, roles module, products modules and errors page, so create number of view like as bellow:

resources/views/layouts/app.blade.php

<html lang="{{ app()->getLocale() }}">
<head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <!-- CSRF Token -->
    <meta name="csrf-token" content="{{ csrf_token() }}">
    <title>{{ config('app.name', 'Laravel 5.8 User Roles and Permissions Tutorial') }}</title>
    <!-- Scripts -->
    <script src="{{ asset('js/app.js') }}" defer></script>
    <!-- Fonts -->
    <link rel="dns-prefetch" href="https://fonts.gstatic.com">
    <link href="https://fonts.googleapis.com/css?family=Raleway:300,400,600" rel="stylesheet" type="text/css">
    <!-- Styles -->
    <link href="{{ asset('css/app.css') }}" rel="stylesheet">
</head>
<body>
    <div id="app">
        <nav class="navbar navbar-expand-md navbar-light navbar-laravel">
            <div class="container">
                <a class="navbar-brand" href="{{ url('/') }}">
                    Laravel 5.8 User Roles and Permissions - ItSolutionStuff.com
                </a>
                <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
                    <span class="navbar-toggler-icon"></span>
                </button>

                <div class="collapse navbar-collapse" id="navbarSupportedContent">
                    <!-- Left Side Of Navbar -->
                    <ul class="navbar-nav mr-auto"></ul>

                    <!-- Right Side Of Navbar -->
                    <ul class="navbar-nav ml-auto">
                        <!-- Authentication Links -->
                        @guest
                            <li><a class="nav-link" href="{{ route('login') }}">{{ __('Login') }}</a></li>
                            <li><a class="nav-link" href="{{ route('register') }}">{{ __('Register') }}</a></li>
                        @else
                            <li><a class="nav-link" href="{{ route('users.index') }}">Manage Users</a></li>
                            <li><a class="nav-link" href="{{ route('roles.index') }}">Manage Role</a></li>
                            <li><a class="nav-link" href="{{ route('products.index') }}">Manage Product</a></li>
                            <li class="nav-item dropdown">
                                <a id="navbarDropdown" class="nav-link dropdown-toggle" href="#" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false" v-pre>
                                    {{ Auth::user()->name }} <span class="caret"></span>
                                </a>

                                <div class="dropdown-menu" aria-labelledby="navbarDropdown">
                                    <a class="dropdown-item" href="{{ route('logout') }}"
                                       onclick="event.preventDefault();
                                                     document.getElementById('logout-form').submit();">
                                        {{ __('Logout') }}
                                    </a>

                                    <form id="logout-form" action="{{ route('logout') }}" method="POST" style="display: none;">
                                        @csrf
                                    </form>
                                </div>
                            </li>
                        @endguest
                    </ul>
                </div>
            </div>
        </nav>

        <main class="py-4">
            <div class="container">
            @yield('content')
            </div>
        </main>
    </div>
</body>
</html>

resources/views/users/index.blade.php

@extends('layouts.app')

@section('content')
<div class="row">
    <div class="col-lg-12 margin-tb">
        <div class="pull-left">
            <h2>Users Management</h2>
        </div>
        <div class="pull-right">
            <a class="btn btn-success" href="{{ route('users.create') }}"> Create New User</a>
        </div>
    </div>
</div>

@if ($message = Session::get('success'))
<div class="alert alert-success">
  <p>{{ $message }}</p>
</div>
@endif

<table class="table table-bordered">
 <tr>
   <th>No</th>
   <th>Name</th>
   <th>Email</th>
   <th>Roles</th>
   <th width="280px">Action</th>
 </tr>
 @foreach ($data as $key => $user)
  <tr>
    <td>{{ ++$i }}</td>
    <td>{{ $user->name }}</td>
    <td>{{ $user->email }}</td>
    <td>
      @if(!empty($user->getRoleNames()))
        @foreach($user->getRoleNames() as $v)
           <label class="badge badge-success">{{ $v }}</label>
        @endforeach
      @endif
    </td>
    <td>
       <a class="btn btn-info" href="{{ route('users.show',$user->id) }}">Show</a>
       <a class="btn btn-primary" href="{{ route('users.edit',$user->id) }}">Edit</a>
        {!! Form::open(['method' => 'DELETE','route' => ['users.destroy', $user->id],'style'=>'display:inline']) !!}
            {!! Form::submit('Delete', ['class' => 'btn btn-danger']) !!}
        {!! Form::close() !!}
    </td>
  </tr>
 @endforeach
</table>

{!! $data->render() !!}

<p class="text-center text-primary"><small>Tutorial by ItSolutionStuff.com</small></p>
@endsection

resources/views/users/create.blade.php

@extends('layouts.app')

@section('content')
<div class="row">
    <div class="col-lg-12 margin-tb">
        <div class="pull-left">
            <h2>Create New User</h2>
        </div>
        <div class="pull-right">
            <a class="btn btn-primary" href="{{ route('users.index') }}"> Back</a>
        </div>
    </div>
</div>

@if (count($errors) > 0)
  <div class="alert alert-danger">
    <strong>Whoops!</strong> There were some problems with your input.<br><br>
    <ul>
       @foreach ($errors->all() as $error)
         <li>{{ $error }}</li>
       @endforeach
    </ul>
  </div>
@endif


{!! Form::open(array('route' => 'users.store','method'=>'POST')) !!}
<div class="row">
    <div class="col-xs-12 col-sm-12 col-md-12">
        <div class="form-group">
            <strong>Name:</strong>
            {!! Form::text('name', null, array('placeholder' => 'Name','class' => 'form-control')) !!}
        </div>
    </div>
    <div class="col-xs-12 col-sm-12 col-md-12">
        <div class="form-group">
            <strong>Email:</strong>
            {!! Form::text('email', null, array('placeholder' => 'Email','class' => 'form-control')) !!}
        </div>
    </div>
    <div class="col-xs-12 col-sm-12 col-md-12">
        <div class="form-group">
            <strong>Password:</strong>
            {!! Form::password('password', array('placeholder' => 'Password','class' => 'form-control')) !!}
        </div>
    </div>
    <div class="col-xs-12 col-sm-12 col-md-12">
        <div class="form-group">
            <strong>Confirm Password:</strong>
            {!! Form::password('confirm-password', array('placeholder' => 'Confirm Password','class' => 'form-control')) !!}
        </div>
    </div>
    <div class="col-xs-12 col-sm-12 col-md-12">
        <div class="form-group">
            <strong>Role:</strong>
            {!! Form::select('roles[]', $roles,[], array('class' => 'form-control','multiple')) !!}
        </div>
    </div>
    <div class="col-xs-12 col-sm-12 col-md-12 text-center">
        <button type="submit" class="btn btn-primary">Submit</button>
    </div>
</div>
{!! Form::close() !!}

<p class="text-center text-primary"><small>Tutorial by ItSolutionStuff.com</small></p>
@endsection

resources/views/users/edit.blade.php

@extends('layouts.app')

@section('content')
<div class="row">
    <div class="col-lg-12 margin-tb">
        <div class="pull-left">
            <h2>Edit New User</h2>
        </div>
        <div class="pull-right">
            <a class="btn btn-primary" href="{{ route('users.index') }}"> Back</a>
        </div>
    </div>
</div>

@if (count($errors) > 0)
  <div class="alert alert-danger">
    <strong>Whoops!</strong> There were some problems with your input.<br><br>
    <ul>
       @foreach ($errors->all() as $error)
         <li>{{ $error }}</li>
       @endforeach
    </ul>
  </div>
@endif

{!! Form::model($user, ['method' => 'PATCH','route' => ['users.update', $user->id]]) !!}
<div class="row">
    <div class="col-xs-12 col-sm-12 col-md-12">
        <div class="form-group">
            <strong>Name:</strong>
            {!! Form::text('name', null, array('placeholder' => 'Name','class' => 'form-control')) !!}
        </div>
    </div>
    <div class="col-xs-12 col-sm-12 col-md-12">
        <div class="form-group">
            <strong>Email:</strong>
            {!! Form::text('email', null, array('placeholder' => 'Email','class' => 'form-control')) !!}
        </div>
    </div>
    <div class="col-xs-12 col-sm-12 col-md-12">
        <div class="form-group">
            <strong>Password:</strong>
            {!! Form::password('password', array('placeholder' => 'Password','class' => 'form-control')) !!}
        </div>
    </div>
    <div class="col-xs-12 col-sm-12 col-md-12">
        <div class="form-group">
            <strong>Confirm Password:</strong>
            {!! Form::password('confirm-password', array('placeholder' => 'Confirm Password','class' => 'form-control')) !!}
        </div>
    </div>
    <div class="col-xs-12 col-sm-12 col-md-12">
        <div class="form-group">
            <strong>Role:</strong>
            {!! Form::select('roles[]', $roles,$userRole, array('class' => 'form-control','multiple')) !!}
        </div>
    </div>
    <div class="col-xs-12 col-sm-12 col-md-12 text-center">
        <button type="submit" class="btn btn-primary">Submit</button>
    </div>
</div>
{!! Form::close() !!}

<p class="text-center text-primary"><small>Tutorial by ItSolutionStuff.com</small></p>
@endsection

resources/views/users/show.blade.php

@extends('layouts.app')

@section('content')
<div class="row">
    <div class="col-lg-12 margin-tb">
        <div class="pull-left">
            <h2> Show User</h2>
        </div>
        <div class="pull-right">
            <a class="btn btn-primary" href="{{ route('users.index') }}"> Back</a>
        </div>
    </div>
</div>

<div class="row">
    <div class="col-xs-12 col-sm-12 col-md-12">
        <div class="form-group">
            <strong>Name:</strong>
            {{ $user->name }}
        </div>
    </div>
    <div class="col-xs-12 col-sm-12 col-md-12">
        <div class="form-group">
            <strong>Email:</strong>
            {{ $user->email }}
        </div>
    </div>
    <div class="col-xs-12 col-sm-12 col-md-12">
        <div class="form-group">
            <strong>Roles:</strong>
            @if(!empty($user->getRoleNames()))
                @foreach($user->getRoleNames() as $v)
                    <label class="badge badge-success">{{ $v }}</label>
                @endforeach
            @endif
        </div>
    </div>
</div>
@endsection

resources/views/roles/index.blade.php

@extends('layouts.app')

@section('content')
<div class="row">
    <div class="col-lg-12 margin-tb">
        <div class="pull-left">
            <h2>Role Management</h2>
        </div>
        <div class="pull-right">
        @can('role-create')
            <a class="btn btn-success" href="{{ route('roles.create') }}"> Create New Role</a>
            @endcan
        </div>
    </div>
</div>

@if ($message = Session::get('success'))
    <div class="alert alert-success">
        <p>{{ $message }}</p>
    </div>
@endif

<table class="table table-bordered">
  <tr>
     <th>No</th>
     <th>Name</th>
     <th width="280px">Action</th>
  </tr>
    @foreach ($roles as $key => $role)
    <tr>
        <td>{{ ++$i }}</td>
        <td>{{ $role->name }}</td>
        <td>
            <a class="btn btn-info" href="{{ route('roles.show',$role->id) }}">Show</a>
            @can('role-edit')
                <a class="btn btn-primary" href="{{ route('roles.edit',$role->id) }}">Edit</a>
            @endcan
            @can('role-delete')
                {!! Form::open(['method' => 'DELETE','route' => ['roles.destroy', $role->id],'style'=>'display:inline']) !!}
                    {!! Form::submit('Delete', ['class' => 'btn btn-danger']) !!}
                {!! Form::close() !!}
            @endcan
        </td>
    </tr>
    @endforeach
</table>

{!! $roles->render() !!}

<p class="text-center text-primary"><small>Tutorial by ItSolutionStuff.com</small></p>
@endsection

resources/views/roles/create.blade.php

@extends('layouts.app')

@section('content')
<div class="row">
    <div class="col-lg-12 margin-tb">
        <div class="pull-left">
            <h2>Create New Role</h2>
        </div>
        <div class="pull-right">
            <a class="btn btn-primary" href="{{ route('roles.index') }}"> Back</a>
        </div>
    </div>
</div>

@if (count($errors) > 0)
    <div class="alert alert-danger">
        <strong>Whoops!</strong> There were some problems with your input.<br><br>
        <ul>
        @foreach ($errors->all() as $error)
            <li>{{ $error }}</li>
        @endforeach
        </ul>
    </div>
@endif

{!! Form::open(array('route' => 'roles.store','method'=>'POST')) !!}
<div class="row">
    <div class="col-xs-12 col-sm-12 col-md-12">
        <div class="form-group">
            <strong>Name:</strong>
            {!! Form::text('name', null, array('placeholder' => 'Name','class' => 'form-control')) !!}
        </div>
    </div>
    <div class="col-xs-12 col-sm-12 col-md-12">
        <div class="form-group">
            <strong>Permission:</strong>
            <br/>
            @foreach($permission as $value)
                <label>{{ Form::checkbox('permission[]', $value->id, false, array('class' => 'name')) }}
                {{ $value->name }}</label>
            <br/>
            @endforeach
        </div>
    </div>
    <div class="col-xs-12 col-sm-12 col-md-12 text-center">
        <button type="submit" class="btn btn-primary">Submit</button>
    </div>
</div>
{!! Form::close() !!}

<p class="text-center text-primary"><small>Tutorial by ItSolutionStuff.com</small></p>
@endsection

resources/views/roles/edit.blade.php

@extends('layouts.app')

@section('content')
<div class="row">
    <div class="col-lg-12 margin-tb">
        <div class="pull-left">
            <h2>Edit Role</h2>
        </div>
        <div class="pull-right">
            <a class="btn btn-primary" href="{{ route('roles.index') }}"> Back</a>
        </div>
    </div>
</div>

@if (count($errors) > 0)
    <div class="alert alert-danger">
        <strong>Whoops!</strong> There were some problems with your input.<br><br>
        <ul>
        @foreach ($errors->all() as $error)
            <li>{{ $error }}</li>
        @endforeach
        </ul>
    </div>
@endif

{!! Form::model($role, ['method' => 'PATCH','route' => ['roles.update', $role->id]]) !!}
<div class="row">
    <div class="col-xs-12 col-sm-12 col-md-12">
        <div class="form-group">
            <strong>Name:</strong>
            {!! Form::text('name', null, array('placeholder' => 'Name','class' => 'form-control')) !!}
        </div>
    </div>
    <div class="col-xs-12 col-sm-12 col-md-12">
        <div class="form-group">
            <strong>Permission:</strong>
            <br/>
            @foreach($permission as $value)
                <label>{{ Form::checkbox('permission[]', $value->id, in_array($value->id, $rolePermissions) ? true : false, array('class' => 'name')) }}
                {{ $value->name }}</label>
            <br/>
            @endforeach
        </div>
    </div>
    <div class="col-xs-12 col-sm-12 col-md-12 text-center">
        <button type="submit" class="btn btn-primary">Submit</button>
    </div>
</div>
{!! Form::close() !!}

@endsection
<p class="text-center text-primary"><small>Tutorial by ItSolutionStuff.com</small></p>

resources/views/roles/show.blade.php

@extends('layouts.app')

@section('content')
<div class="row">
    <div class="col-lg-12 margin-tb">
        <div class="pull-left">
            <h2> Show Role</h2>
        </div>
        <div class="pull-right">
            <a class="btn btn-primary" href="{{ route('roles.index') }}"> Back</a>
        </div>
    </div>
</div>

<div class="row">
    <div class="col-xs-12 col-sm-12 col-md-12">
        <div class="form-group">
            <strong>Name:</strong>
            {{ $role->name }}
        </div>
    </div>
    <div class="col-xs-12 col-sm-12 col-md-12">
        <div class="form-group">
            <strong>Permissions:</strong>
            @if(!empty($rolePermissions))
                @foreach($rolePermissions as $v)
                    <label class="label label-success">{{ $v->name }},</label>
                @endforeach
            @endif
        </div>
    </div>
</div>
@endsection

resources/views/products/index.blade.php

@extends('layouts.app')

@section('content')
    <div class="row">
        <div class="col-lg-12 margin-tb">
            <div class="pull-left">
                <h2>Products</h2>
            </div>
            <div class="pull-right">
                @can('product-create')
                <a class="btn btn-success" href="{{ route('products.create') }}"> Create New Product</a>
                @endcan
            </div>
        </div>
    </div>

    @if ($message = Session::get('success'))
        <div class="alert alert-success">
            <p>{{ $message }}</p>
        </div>
    @endif

    <table class="table table-bordered">
        <tr>
            <th>No</th>
            <th>Name</th>
            <th>Details</th>
            <th width="280px">Action</th>
        </tr>
	    @foreach ($products as $product)
	    <tr>
	        <td>{{ ++$i }}</td>
	        <td>{{ $product->name }}</td>
	        <td>{{ $product->detail }}</td>
	        <td>
                <form action="{{ route('products.destroy',$product->id) }}" method="POST">
                    <a class="btn btn-info" href="{{ route('products.show',$product->id) }}">Show</a>
                    @can('product-edit')
                    <a class="btn btn-primary" href="{{ route('products.edit',$product->id) }}">Edit</a>
                    @endcan

                    @csrf
                    @method('DELETE')
                    @can('product-delete')
                    <button type="submit" class="btn btn-danger">Delete</button>
                    @endcan
                </form>
	        </td>
	    </tr>
	    @endforeach
    </table>

    {!! $products->links() !!}

<p class="text-center text-primary"><small>Tutorial by ItSolutionStuff.com</small></p>
@endsection

resources/views/products/create.blade.php

@extends('layouts.app')

@section('content')
    <div class="row">
        <div class="col-lg-12 margin-tb">
            <div class="pull-left">
                <h2>Add New Product</h2>
            </div>
            <div class="pull-right">
                <a class="btn btn-primary" href="{{ route('products.index') }}"> Back</a>
            </div>
        </div>
    </div>

    @if ($errors->any())
        <div class="alert alert-danger">
            <strong>Whoops!</strong> There were some problems with your input.<br><br>
            <ul>
                @foreach ($errors->all() as $error)
                    <li>{{ $error }}</li>
                @endforeach
            </ul>
        </div>
    @endif

    <form action="{{ route('products.store') }}" method="POST">
    	@csrf

         <div class="row">
		    <div class="col-xs-12 col-sm-12 col-md-12">
		        <div class="form-group">
		            <strong>Name:</strong>
		            <input type="text" name="name" class="form-control" placeholder="Name">
		        </div>
		    </div>
		    <div class="col-xs-12 col-sm-12 col-md-12">
		        <div class="form-group">
		            <strong>Detail:</strong>
		            <textarea class="form-control" style="height:150px" name="detail" placeholder="Detail"></textarea>
		        </div>
		    </div>
		    <div class="col-xs-12 col-sm-12 col-md-12 text-center">
		            <button type="submit" class="btn btn-primary">Submit</button>
		    </div>
		</div>

    </form>

<p class="text-center text-primary"><small>Tutorial by ItSolutionStuff.com</small></p>
@endsection

resources/views/products/edit.blade.php

@extends('layouts.app')

@section('content')
    <div class="row">
        <div class="col-lg-12 margin-tb">
            <div class="pull-left">
                <h2>Edit Product</h2>
            </div>
            <div class="pull-right">
                <a class="btn btn-primary" href="{{ route('products.index') }}"> Back</a>
            </div>
        </div>
    </div>

    @if ($errors->any())
        <div class="alert alert-danger">
            <strong>Whoops!</strong> There were some problems with your input.<br><br>
            <ul>
                @foreach ($errors->all() as $error)
                    <li>{{ $error }}</li>
                @endforeach
            </ul>
        </div>
    @endif

    <form action="{{ route('products.update',$product->id) }}" method="POST">
    	@csrf
        @method('PUT')

         <div class="row">
		    <div class="col-xs-12 col-sm-12 col-md-12">
		        <div class="form-group">
		            <strong>Name:</strong>
		            <input type="text" name="name" value="{{ $product->name }}" class="form-control" placeholder="Name">
		        </div>
		    </div>
		    <div class="col-xs-12 col-sm-12 col-md-12">
		        <div class="form-group">
		            <strong>Detail:</strong>
		            <textarea class="form-control" style="height:150px" name="detail" placeholder="Detail">{{ $product->detail }}</textarea>
		        </div>
		    </div>
		    <div class="col-xs-12 col-sm-12 col-md-12 text-center">
		      <button type="submit" class="btn btn-primary">Submit</button>
		    </div>
		</div>

    </form>

<p class="text-center text-primary"><small>Tutorial by ItSolutionStuff.com</small></p>
@endsection

resources/views/products/show.blade.php

@extends('layouts.app')

@section('content')
    <div class="row">
        <div class="col-lg-12 margin-tb">
            <div class="pull-left">
                <h2> Show Product</h2>
            </div>
            <div class="pull-right">
                <a class="btn btn-primary" href="{{ route('products.index') }}"> Back</a>
            </div>
        </div>
    </div>

    <div class="row">
        <div class="col-xs-12 col-sm-12 col-md-12">
            <div class="form-group">
                <strong>Name:</strong>
                {{ $product->name }}
            </div>
        </div>
        <div class="col-xs-12 col-sm-12 col-md-12">
            <div class="form-group">
                <strong>Details:</strong>
                {{ $product->detail }}
            </div>
        </div>
    </div>
@endsection
<p class="text-center text-primary"><small>Tutorial by ItSolutionStuff.com</small></p>

Step 10: Handle Exertion Error

Now, in this step we will handle exertion. if you don't have a permission and try to access that page using browser url then you can give message as like bellow:

add/Exceptions/Handler.php

......
public function render($request, Exception $exception)
{
    if ($exception instanceof \Spatie\Permission\Exceptions\UnauthorizedException) {
        return response()->json(['User have not permission for this page access.']);
    }
 
    return parent::render($request, $exception);
}
....

Step 11: Create Seeder For Permissions and AdminUser

In this step we will create seeder for permissions, Right now we have fixed permission so we create using seeder as listed bellow, but if you can add more permission as you want:

1.role-list

2.role-create

3.role-edit

4.role-delete

5.product-list

6.product-create

7.product-edit

8.product-delete

So, first create seeder using bellow command:

php artisan make:seeder PermissionTableSeeder

And put bellow code in PermissionTableSeeder seeder this way:

database/seeds/PermissionTableSeeder.php

<?php

use Illuminate\Database\Seeder;
use Spatie\Permission\Models\Permission;

class PermissionTableSeeder extends Seeder
{
    /**
     * Run the database seeds.
     *
     * @return void
     */
    public function run()
    {
       $permissions = [
           'role-list',
           'role-create',
           'role-edit',
           'role-delete',
           'product-list',
           'product-create',
           'product-edit',
           'product-delete'
        ];

        foreach ($permissions as $permission) {
             Permission::create(['name' => $permission]);
        }
    }
}

After this we have to run bellow command for run PermissionTableSeeder seeder:

php artisan db:seed --class=PermissionTableSeeder

Now let's create new seeder for creating admin user.

php artisan make:seeder CreateAdminUserSeeder

database/seeds/PermissionTableSeeder.php

<?php
  
use Illuminate\Database\Seeder;
use App\User;
use Spatie\Permission\Models\Role;
use Spatie\Permission\Models\Permission;
  
class CreateAdminUserSeeder extends Seeder
{
    /**
     * Run the database seeds.
     *
     * @return void
     */
    public function run()
    {
        $user = User::create([
        	'name' => 'Hardik Savani', 
        	'email' => '[email protected]',
        	'password' => bcrypt('123456')
        ]);
  
        $role = Role::create(['name' => 'Admin']);
   
        $permissions = Permission::pluck('id','id')->all();
  
        $role->syncPermissions($permissions);
   
        $user->assignRole([$role->id]);
    }
}
php artisan db:seed --class=CreateAdminUserSeeder

Now we are ready to to run full example of ACL. so let's run our example so run bellow command for quick run:

php artisan serve

Access By

http://localhost:8000/

Now you can login with following credential:

Email: [email protected]
Password: 123456

You can see bellow screenshots:

You can download code from GitHub

Creating a Modal Dialog in Angular 8 with TypeScript

Creating a Modal Dialog in Angular 8 with TypeScript

In this tutorial we'll cover how to implement modal windows (dialog boxes) in Angular 8 with TypeScript. The example is a custom modal without the need for any 3rd party libraries.

There are plenty of plugins and libraries out there that include modal windows, in the past I used them myself when I needed to add a modal to a new project. The main issue I have with 3rd party plugins is that they usually contain a lot of features I don't need which adds unnecessary bloat to my Angular app, so a while ago I took some time to implement a custom modal window to see how difficult it would be and also to remove the magic & mystery I had in my mind about exactly how modals work.

When I finished I was pleasantly surprised at the relatively small amount of code required to implement a custom modal window, most of the modal 'magic' is done with a handful of CSS styles (see modal.component.less) while Angular / TypeScript is just used for showing and hiding the modal windows.

Running the Angular 8 Modal Dialog Locally
  1. Install NodeJS and NPM from https://nodejs.org/en/download/.
  2. Download or clone the project source code from https://github.com/cornflourblue/angular-8-custom-modal
  3. Install all required npm packages by running npm install from the command line in the project root folder (where the package.json is located).
  4. Start the application by running npm start from the command line in the project root folder.

NOTE: You can also run the app directly using the Angular CLI command ng serve --open. To do this first install the Angular CLI globally on your system with the command npm install -g @angular/cli.

Adding Custom Modals to Your Angular 8 App

To add modals to your Angular 8 application you'll need to copy the /src/app/_modal folder and contents from the example project, the folder contains the modal module and associated files, including:

  • modal.model.less - LESS/CSS styles for displaying modal dialogs, this is where the modal "magic" happens.
  • modal.component.html - modal component template that contains the wrapper html for displaying modal dialogs.
  • modal.component.ts - modal component with the logic for displaying modal dialogs.
  • modal.module.ts - modal module that encapsulates the modal component so it can be imported by the app module.
  • modal.service.ts - modal service that can be used by any angular component to open and close modal dialogs.
  • index.ts - barrel file that re-exports the modal module and service so they can be imported using only the folder path instead of the full path to each file, and also enables importing from multiple files with a single import.

Import the Modal Module into your App Module

To make the modal component available to your Angular 8 application you need to add the ModalModule to the imports array of your App Module (app.module.ts). See the app module from the example app below, the modal module is imported on line 5 and added to the imports array of the app module on line 16.

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { FormsModule } from '@angular/forms';

import { ModalModule } from './_modal';
import { appRoutingModule } from './app.routing';

import { AppComponent } from './app.component';
import { HomeComponent } from './home';
import { TestPageComponent } from './test-page';

@NgModule({
    imports: [
        BrowserModule,
        FormsModule,
        ModalModule,
        appRoutingModule
    ],
    declarations: [
        AppComponent,
        HomeComponent,
        TestPageComponent
    ],
    bootstrap: [AppComponent]
})

export class AppModule { }

Add the tag to pages where you want to display modals

To add a modal dialog to any page simply add the <jw-modal id="[insert unique id]"></jw-modal> tag along with the content for the modal. You can put any content you like inside the <jw-modal> element. You can also update the modal LESS/CSS if you want to change the styles of the modals, e.g to make them smaller or add CSS animation transitions.

IMPORTANT: A unique id is required for each modal on a page, it can be any string e.g. 'custom-modal-1'. The id string is used by the modal service to keep track of each active modal in the angular app, so the service knows which modal to open/close based on the id passed to the modalService.open() and modalService.close() methods e.g. modalService.open('custom-modal-1').

Here is the home component template from the example app (/src/app/home/home.component.html) that contains two modals, each is opened by a button click, and the first modal contains an input text field that allows you to edit the bodyText displayed in the template.

<div>
    <h1>Home</h1>
    <p>{{bodyText}}</p>
    <button (click)="openModal('custom-modal-1')">Open Modal 1</button>
    <button (click)="openModal('custom-modal-2')">Open Modal 2</button>
</div>

<jw-modal id="custom-modal-1">
    <h1>A Custom Modal!</h1>
    <p>Home page text: <input type="text" [(ngModel)]="bodyText" /></p>
    <button (click)="closeModal('custom-modal-1');">Close</button>
</jw-modal>

<jw-modal id="custom-modal-2">
    <h1 style="height:1000px">A Tall Custom Modal!</h1>
    <button (click)="closeModal('custom-modal-2');">Close</button>
</jw-modal>	

Opening & Closing Angular 8 Modal Dialogs

To open a modal call the modalService.open() method with the id of the modal you want to open, e.g. modalService.open('custom-modal-1'). To close a modal call the modalService.close() method with the id of the modal you want to close, e.g. modalService.close('custom-modal-1').

By default modals are closed on background click, to disable this remove the chunk of code in the modal component (/src/app/_modal/modal.component.ts) located directly below the comment // close modal on background click.

Here is the home component from the example app (/src/app/home/home.component.ts), it contains methods for opening and closing modals (openModal() and closeModal()) that call the corresponding methods of the modal service.

import { Component, OnInit } from '@angular/core';

import { ModalService } from '../_modal';

@Component({ templateUrl: 'home.component.html' })
export class HomeComponent implements OnInit {
    bodyText: string;

    constructor(private modalService: ModalService) { }

    ngOnInit() {
        this.bodyText = 'This text can be updated in modal 1';
    }

    openModal(id: string) {
        this.modalService.open(id);
    }

    closeModal(id: string) {
        this.modalService.close(id);
    }
}	
Breakdown of the Angular 8 Custom Modal Code

Below is a breakdown of the pieces of code used to implement custom modal dialogs in Angular 8 & TypeScript, you don't need to know the details of how it all works to use the modals in your project, it's only if you're interested in the nuts and bolts or if you want to modify the underlying code or behaviour.

LESS/CSS Styles for Angular 8 Modal Dialogs

These are the styles applied to the custom modal dialogs in this example, they could also be used in non-angular projects as it's just pure LESS/CSS.

I prefixed the modal element and classes with jw- to prevent conflicts with 3rd party css libraries such as Bootstrap.

/* MODAL STYLES
-------------------------------*/
jw-modal {
    /* modals are hidden by default */
    display: none;

    .jw-modal {
        /* modal container fixed across whole screen */
        position: fixed;
        top: 0;
        right: 0;
        bottom: 0;
        left: 0;

        /* z-index must be higher than .jw-modal-background */
        z-index: 1000;
        
        /* enables scrolling for tall modals */
        overflow: auto;

        .jw-modal-body {
            padding: 20px;
            background: #fff;

            /* margin exposes part of the modal background */
            margin: 40px;
        }
    }

    .jw-modal-background {
        /* modal background fixed across whole screen */
        position: fixed;
        top: 0;
        right: 0;
        bottom: 0;
        left: 0;

        /* semi-transparent black  */
        background-color: #000;
        opacity: 0.75;
        
        /* z-index must be below .jw-modal and above everything else  */
        z-index: 900;
    }
}

body.jw-modal-open {
    /* body overflow is hidden to hide main scrollbar when modal window is open */
    overflow: hidden;
}	
Angular 8 Modal Service

The Angular 8 modal service manages the communication that's required between page components and modal components. It maintains a list of available modals on the page and exposes methods for interacting with those modals.

import { Injectable } from '@angular/core';

@Injectable({ providedIn: 'root' })
export class ModalService {
    private modals: any[] = [];

    add(modal: any) {
        // add modal to array of active modals
        this.modals.push(modal);
    }

    remove(id: string) {
        // remove modal from array of active modals
        this.modals = this.modals.filter(x => x.id !== id);
    }

    open(id: string) {
        // open modal specified by id
        const modal = this.modals.find(x => x.id === id);
        modal.open();
    }

    close(id: string) {
        // close modal specified by id
        const modal = this.modals.find(x => x.id === id);
        modal.close();
    }
}	
Angular 8 Modal Component

The custom modal component is used to add modal windows anywhere in your angular application by using the <jw-modal> tag. Each modal instance adds itself to the modal service when it loads by calling modalService.add(this) from the ngOnInit Angular lifecycle method, and removes itself from the modal service when it is destroyed by calling modalService.remove(this.id) from the ngOnDestroy Angular lifecycle method.

import { Component, ViewEncapsulation, ElementRef, Input, OnInit, OnDestroy } from '@angular/core';

import { ModalService } from './modal.service';

@Component({ 
    selector: 'jw-modal', 
    templateUrl: 'modal.component.html', 
    styleUrls: ['modal.component.less'],
    encapsulation: ViewEncapsulation.None
})
export class ModalComponent implements OnInit, OnDestroy {
    @Input() id: string;
    private element: any;

    constructor(private modalService: ModalService, private el: ElementRef) {
        this.element = el.nativeElement;
    }

    ngOnInit(): void {
        // ensure id attribute exists
        if (!this.id) {
            console.error('modal must have an id');
            return;
        }

        // move element to bottom of page (just before </body>) so it can be displayed above everything else
        document.body.appendChild(this.element);

        // close modal on background click
        this.element.addEventListener('click', el => {
            if (el.target.className === 'jw-modal') {
                this.close();
            }
        });

        // add self (this modal instance) to the modal service so it's accessible from controllers
        this.modalService.add(this);
    }

    // remove self from modal service when component is destroyed
    ngOnDestroy(): void {
        this.modalService.remove(this.id);
        this.element.remove();
    }

    // open modal
    open(): void {
        this.element.style.display = 'block';
        document.body.classList.add('jw-modal-open');
    }

    // close modal
    close(): void {
        this.element.style.display = 'none';
        document.body.classList.remove('jw-modal-open');
    }
}	
Angular 8 Modal Component Template

The modal component template contains just a couple of wrapper divs for the modal content and a div for the modal background. The <ng-content> element is replaced by Angular with the contents you set inside the <jw-modal> element, this is called Angular content projection.

<div class="jw-modal">
    <div class="jw-modal-body">
        <ng-content></ng-content>
    </div>
</div>
<div class="jw-modal-background"></div>	

Thanks for reading

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Further reading about AngularJS

Angular 8 (formerly Angular 2) - The Complete Guide

Angular & NodeJS - The MEAN Stack Guide

The Complete Node.js Developer Course (3rd Edition)

The Web Developer Bootcamp

Best 50 Angular Interview Questions for Frontend Developers in 2019

MEAN Stack Angular 8 CRUD Web Application

Angular 8 Tutorial - User Registration and Login Example

How to build a CRUD Web App with Angular 8.0

Building CRUD Mobile App using Ionic 4, Angular 8

Angular 8 Material Design Tutorial & Example

How to Set up an SMS Notification With Python

How to Set up an SMS Notification With Python

How to Set up an SMS Notification With Python. oday I am beginning a new series of posts specifically aimed at Python beginners.

Hi everyone :) Today I am beginning a new series of posts specifically aimed at Python beginners. The concept is rather simple: I'll do a fun project, in as few lines of code as possible, and will try out as many new tools as possible.

For example, today we will learn to use the Twilio API, the Twitch API, and we'll see how to deploy the project on Heroku. I'll show you how you can have your own "Twitch Live" SMS notifier, in 30 lines of codes, and for 12 cents a month.

Prerequisite: You only need to know how to run Python on your machine and some basic commands in git (commit & push). If you need help with these, I can recommend these 2 articles to you:

Python 3 Installation & Setup Guide

The Ultimate Git Command Tutorial for Beginners from Adrian Hajdin.

What you'll learn:

  • Twitch API
  • Twilio API
  • Deploying on Heroku
  • Setting up a scheduler on Heroku

What you will build:

The specifications are simple: we want to receive an SMS as soon as a specific Twitcher is live streaming. We want to know when this person is going live and when they leave streaming. We want this whole thing to run by itself, all day long.

We will split the project into 3 parts. First, we will see how to programmatically know if a particular Twitcher is online. Then we will see how to receive an SMS when this happens. We will finish by seeing how to make this piece of code run every X minutes, so we never miss another moment of our favorite streamer's life.

Is this Twitcher live?

To know if a Twitcher is live, we can do two things: we can go to the Twitcher URL and try to see if the badge "Live" is there.

Screenshot of a Twitcher live streaming.

This process involves scraping and is not easily doable in Python in less than 20 or so lines of code. Twitch runs a lot of JS code and a simple request.get() won't be enough.

For scraping to work, in this case, we would need to scrape this page inside Chrome to get the same content like what you see in the screenshot. This is doable, but it will take much more than 30 lines of code. If you'd like to learn more, don't hesitate to check my recent web scraping guide.

So instead of trying to scrape Twitch, we will use their API. For those unfamiliar with the term, an API is a programmatic interface that allows websites to expose their features and data to anyone, mainly developers. In Twitch's case, their API is exposed through HTTP, witch means that we can have lots of information and do lots of things by just making a simple HTTP request.

Get your API key

To do this, you have to first create a Twitch API key. Many services enforce authentication for their APIs to ensure that no one abuses them or to restrict access to certain features by certain people.

Please follow these steps to get your API key:

  • Create a Twitch account
  • Now create a Twitch dev account -> "Signing up with Twitch" top right
  • Go to your "dashboard" once logged in
  • "Register your application"
  • Name -> Whatever, Oauth redirection URL -> http://localhost, Category -> Whatever

You should now see, at the bottom of your screen, your client-id. Keep this for later.

Is that Twitcher streaming now?

With your API key in hand, we can now query the Twitch API to have the information we want, so let's begin to code. The following snippet just consumes the Twitch API with the correct parameters and prints the response.

# requests is the go to package in python to make http request
# https://2.python-requests.org/en/master/
import requests

# This is one of the route where Twich expose data, 
# They have many more: https://dev.twitch.tv/docs
endpoint = "https://api.twitch.tv/helix/streams?"

# In order to authenticate we need to pass our api key through header
headers = {"Client-ID": "<YOUR-CLIENT-ID>"}

# The previously set endpoint needs some parameter, here, the Twitcher we want to follow
# Disclaimer, I don't even know who this is, but he was the first one on Twich to have a live stream so I could have nice examples
params = {"user_login": "Solary"}

# It is now time to make the actual request
response = request.get(endpoint, params=params, headers=headers)
print(response.json())

The output should look like this:

{
   'data':[
      {
         'id':'35289543872',
         'user_id':'174955366',
         'user_name':'Solary',
         'game_id':'21779',
         'type':'live',
         'title':"Wakz duoQ w/ Tioo - GM 400LP - On récupère le chall après les -250LP d'inactivité !",
         'viewer_count':4073,
         'started_at':'2019-08-14T07:01:59Z',
         'language':'fr',
         'thumbnail_url':'https://static-cdn.jtvnw.net/previews-ttv/live_user_solary-{width}x{height}.jpg',
         'tag_ids':[
            '6f655045-9989-4ef7-8f85-1edcec42d648'
         ]
      }
   ],
   'pagination':{
      'cursor':'eyJiIjpudWxsLCJhIjp7Ik9mZnNldCI6MX19'
   }
}

This data format is called JSON and is easily readable. The data object is an array that contains all the currently active streams. The key type ensures that the stream is currently live. This key will be empty otherwise (in case of an error, for example).

So if we want to create a boolean variable in Python that stores whether the current user is streaming, all we have to append to our code is:

json_response = response.json()

# We get only streams
streams = json_response.get('data', [])

# We create a small function, (a lambda), that tests if a stream is live or not
is_active = lambda stream: stream.get('type') == 'live'
# We filter our array of streams with this function so we only keep streams that are active
streams_active = filter(is_active, streams)

# any returns True if streams_active has at least one element, else False
at_least_one_stream_active = any(streams_active)

print(at_least_one_stream_active)

At this point, at_least_one_stream_active is True when your favourite Twitcher is live.

Let's now see how to get notified by SMS.

Send me a text, NOW!

So to send a text to ourselves, we will use the Twilio API. Just go over there and create an account. When asked to confirm your phone number, please use the phone number you want to use in this project. This way you'll be able to use the $15 of free credit Twilio offers to new users. At around 1 cent a text, it should be enough for your bot to run for one year.

If you go on the console, you'll see your Account SID and your Auth Token , save them for later. Also click on the big red button "Get My Trial Number", follow the step, and save this one for later too.

Sending a text with the Twilio Python API is very easy, as they provide a package that does the annoying stuff for you. Install the package with pip install Twilio and just do:

from twilio.rest import Client
client = Client(<Your Account SID>, <Your Auth Token>)
client.messages.create(
	body='Test MSG',from_=<Your Trial Number>,to=<Your Real Number>)

And that is all you need to send yourself a text, amazing right?

Putting everything together

We will now put everything together, and shorten the code a bit so we manage to say under 30 lines of Python code.

import requests
from twilio.rest import Client
endpoint = "https://api.twitch.tv/helix/streams?"
headers = {"Client-ID": "<YOUR-CLIENT-ID>"}
params = {"user_login": "Solary"}
response = request.get(endpoint, params=params, headers=headers)
json_response = response.json()
streams = json_response.get('data', [])
is_active = lambda stream:stream.get('type') == 'live'
streams_active = filter(is_active, streams)
at_least_one_stream_active = any(streams_active)
if at_least_one_stream_active:
    client = Client(<Your Account SID>, <Your Auth Token>)
	client.messages.create(body='LIVE !!!',from_=<Your Trial Number>,to=<Your Real Number>)

Avoiding double notifications

This snippet works great, but should that snippet run every minute on a server, as soon as our favorite Twitcher goes live we will receive an SMS every minute.

We need a way to store the fact that we were already notified that our Twitcher is live and that we don't need to be notified anymore.

The good thing with the Twilio API is that it offers a way to retrieve our message history, so we just have to retrieve the last SMS we sent to see if we already sent a text notifying us that the twitcher is live.

Here what we are going do to in pseudocode:

if favorite_twitcher_live and last_sent_sms is not live_notification:
	send_live_notification()
if not favorite_twitcher_live and last_sent_sms is live_notification:
	send_live_is_over_notification()

This way we will receive a text as soon as the stream starts, as well as when it is over. This way we won't get spammed - perfect right? Let's code it:

# reusing our Twilio client
last_messages_sent = client.messages.list(limit=1)
last_message_id = last_messages_sent[0].sid
last_message_data = client.messages(last_message_id).fetch()
last_message_content = last_message_data.body

Let's now put everything together again:

import requests
from twilio.rest import Client
client = Client(<Your Account SID>, <Your Auth Token>)

endpoint = "https://api.twitch.tv/helix/streams?"
headers = {"Client-ID": "<YOUR-CLIENT-ID>"}
params = {"user_login": "Solary"}
response = request.get(endpoint, params=params, headers=headers)
json_response = response.json()
streams = json_response.get('data', [])
is_active = lambda stream:stream.get('type') == 'live'
streams_active = filter(is_active, streams)
at_least_one_stream_active = any(streams_active)

last_messages_sent = client.messages.list(limit=1)
if last_messages_sent:
	last_message_id = last_messages_sent[0].sid
	last_message_data = client.messages(last_message_id).fetch()
	last_message_content = last_message_data.body
    online_notified = "LIVE" in last_message_content
    offline_notified = not online_notified
else:
	online_notified, offline_notified = False, False

if at_least_one_stream_active and not online_notified:
	client.messages.create(body='LIVE !!!',from_=<Your Trial Number>,to=<Your Real Number>)
if not at_least_one_stream_active and not offline_notified:
	client.messages.create(body='OFFLINE !!!',from_=<Your Trial Number>,to=<Your Real Number>)

And voilà!

You now have a snippet of code, in less than 30 lines of Python, that will send you a text a soon as your favourite Twitcher goes Online / Offline and without spamming you.

We just now need a way to host and run this snippet every X minutes.

The quest for a host

To host and run this snippet we will use Heroku. Heroku is honestly one of the easiest ways to host an app on the web. The downside is that it is really expensive compared to other solutions out there. Fortunately for us, they have a generous free plan that will allow us to do what we want for almost nothing.

If you don't already, you need to create a Heroku account. You also need to download and install the Heroku client.

You now have to move your Python script to its own folder, don't forget to add a requirements.txt file in it. The content of the latter begins:

requests
twilio

This is to ensure that Heroku downloads the correct dependencies.

cd into this folder and just do a heroku create --app <app name>.

If you go on your app dashboard you'll see your new app.

We now need to initialize a git repo and push the code on Heroku:

git init
heroku git:remote -a <app name>
git add .
git commit -am 'Deploy breakthrough script'
git push heroku master

Your app is now on Heroku, but it is not doing anything. Since this little script can't accept HTTP requests, going to <app name>.herokuapp.com won't do anything. But that should not be a problem.

To have this script running 24/7 we need to use a simple Heroku add-on call "Heroku Scheduler". To install this add-on, click on the "Configure Add-ons" button on your app dashboard.

Then, on the search bar, look for Heroku Scheduler:

Click on the result, and click on "Provision"

If you go back to your App dashboard, you'll see the add-on:

Click on the "Heroku Scheduler" link to configure a job. Then click on "Create Job". Here select "10 minutes", and for run command select python <name_of_your_script>.py. Click on "Save job".

While everything we used so far on Heroku is free, the Heroku Scheduler will run the job on the $25/month instance, but prorated to the second. Since this script approximately takes 3 seconds to run, for this script to run every 10 minutes you should just have to spend 12 cents a month.

Ideas for improvements

I hope you liked this project and that you had fun putting it into place. In less than 30 lines of code, we did a lot, but this whole thing is far from perfect. Here are a few ideas to improve it:

  • Send yourself more information about the current streaming (game played, number of viewers ...)
  • Send yourself the duration of the last stream once the twitcher goes offline
  • Don't send you a text, but rather an email
  • Monitor multiple twitchers at the same time

Do not hesitate to tell me in the comments if you have more ideas.

Conclusion

I hope that you liked this post and that you learned things reading it. I truly believe that this kind of project is one of the best ways to learn new tools and concepts, I recently launched a web scraping API where I learned a lot while making it.

Please tell me in the comments if you liked this format and if you want to do more.

I have many other ideas, and I hope you will like them. Do not hesitate to share what other things you build with this snippet, possibilities are endless.

Happy Coding.

Pierre

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