Angular 8 DOM Queries: ViewChild and ViewChildren Example

Angular 8 DOM Queries: ViewChild and ViewChildren Example

Originally published at techiediaries.com

In this tutorial, we'll see an Angular 8 example of how to use the two decorators.

You can use ViewChild if you need to query one element from the DOM and ViewChildren for multiple elements.

We'll be using an online development IDE available from https://stackblitz.com/ so you don't need to set up your local development machine for Angular at this point.

Head over to Stackblitz, sign in with your GitHub account and choose an Angular workspace:

You should be presented with an online IDE with an Angular 8 project:

Our Angular project contains the usual App component and a child component called HelloComponentand defined in the src/app/hello.component.ts file with the followign code:

<pre class="ql-syntax" spellcheck="false">import { Component, Input } from '@angular/core';

@Component({
selector: 'hello',
template: &lt;h1&gt;Hello !&lt;/h1&gt;,
styles: [h1 { font-family: Lato; }]
})
export class HelloComponent {
@Input() name: string;
}
</pre>

The component accepts a name property and uses an inline template which simply displays the value passed via the name property from the parent component.

In the component decorator, we used hello as the selector for the component so in the the HTML template of the App component defined in the src/app/app.component.html file, we include the child component using the following code:

<pre class="ql-syntax" spellcheck="false"><hello name=""></hello>
<p>
Start editing to see some magic happen :)
</p>
</pre>

After running our Angular application the hello component is rendered and becomes part of the DOM so we can query it just like any normal DOM element.

What's ViewChild in Angular?

ViewChild is a decorator that creates a view or DOM query. According to the docs

Property decorator that configures a view query. The change detector looks for the first element or the directive matching the selector in the view DOM. If the view DOM changes, and a new child matches the selector, the property is updated.

The decorator takes the following meta information:

  • selector - the selector of the element to query. This can be a directive type or a name.
  • read - read a different token from the queried elements.
  • static - This is new in Angular 8 and indicates whether or not to resolve query results before change detection runs.

ViewChild can take the following selectors:

  • Classes with the @Component or @Directive decorators i.e components and directives,
  • Template reference variables,
  • Providers,
  • TemplateRef

Now, let's go back to our src/app/app.component.ts file and let's see how we can query the child component using ViewChild. First, change the code accordingly:

<pre class="ql-syntax" spellcheck="false">import { Component, ViewChild, AfterViewInit } from '@angular/core';

import { HelloComponent } from './hello.component';

@Component({
selector: 'my-app',
templateUrl: './app.component.html',
styleUrls: [ './app.component.css' ]
})
export class AppComponent implements AfterViewInit {
name = 'Angular';
@ViewChild(HelloComponent, {static: false}) hello: HelloComponent;

ngAfterViewInit() {
console.log('Hello ', this.hello.name);
}
}
</pre>

In the console, you should get Hello Angular:

Now, let's explain the code.

First, we imported HelloComponent and ViewChild and AfterViewInit from the @angular/corepackage:

<pre class="ql-syntax" spellcheck="false">import { Component, ViewChild, AfterViewInit } from '@angular/core';
import { HelloComponent } from './hello.component';
</pre>

Next, we create a query called hello that takes HelloComponent as the selector and has static equals to false:

<pre class="ql-syntax" spellcheck="false">@ViewChild(HelloComponent, {static: false}) hello: HelloComponent;
</pre>

In Angular 8, timing for ContentChild and ViewChild needs to be specified explicitly.

See: ​Why do I have to specify {static: false}? Isn't that the default?

Next, in the ngAfterViewInit() life-cycle hook, we can use the query to access the DOM element for the hello component. In our example, we accessed the name property of the component, after it's mounted in the DOM, which contains the Angular string:

<pre class="ql-syntax" spellcheck="false">ngAfterViewInit() {
console.log('Hello ', this.hello.name);
}
</pre>

We can access any properties and even methods from the queried component.

Note: View queries are set before the ngAfterViewInit callback is called.

Querying Standard HTML Elements with Template References

We can also query standard HTML elements using ViewChild and template reference variables. Let's go back to our src/app/app.component.html file and change it as follows:

<pre class="ql-syntax" spellcheck="false"><hello name=""></hello>

<p #pRef>
Start editing to see some magic happen :)
</p>
</pre>

We simply added the helloRef template reference to our hello component. Now let's change our code to access the component using its reference. Go back to the src/app/app.component.ts file and change accordingly:

<pre class="ql-syntax" spellcheck="false">import { Component, ViewChild, AfterViewInit, ElementRef } from '@angular/core';

import { HelloComponent } from './hello.component';

@Component({
selector: 'my-app',
templateUrl: './app.component.html',
styleUrls: [ './app.component.css' ]
})
export class AppComponent implements AfterViewInit {
name = 'Angular';
@ViewChild(HelloComponent, {static: false}) hello: HelloComponent;

@ViewChild('pRef', {static: false}) pRef: ElementRef;

ngAfterViewInit() {
console.log(this.pRef.nativeElement.innerHTML); 
this.pRef.nativeElement.innerHTML = "DOM updated successfully!!!"; 

}
}
</pre>

We import ElementRef and we create a query configuration to access the <p> DOM element with the #pRef template reference as follows:

<pre class="ql-syntax" spellcheck="false">@ViewChild('pRef', {static: false}) pRef: ElementRef;
</pre>

Next, in the ngAfterViewInit() method we can access and modify the native DOM element using the nativeElement object of ElementRef:

<pre class="ql-syntax" spellcheck="false"> @ViewChild('pRef', {static: false}) pRef: ElementRef;

ngAfterViewInit() {
console.log(this.pRef.nativeElement.innerHTML);
this.pRef.nativeElement.innerHTML = "DOM updated successfully!!!"; 

}
</pre>

This is the live example from this link.

What's ViewChildren in Angular?

ViewChildren is another property decorator which is used to query the DOM for multiple elements and return a QueryList.

According to the docs:

You can use ViewChildren to get the QueryList of elements or directives from the view DOM. Any time a child element is added, removed, or moved, the query list will be updated, and the changes observable of the query list will emit a new value.

Let's see an example.

Go to the src/app/app.component.html file and update it as follows:

<pre class="ql-syntax" spellcheck="false"><hello name="Angular 6" ></hello>
<hello name="Angular 7" ></hello>
<hello name="Angular 8" ></hello>
</pre>

We are simply diplsaying the hello component three times. Let's now query the DOM. Open the src/app/app.component.ts file and change it as follows:

<pre class="ql-syntax" spellcheck="false">import { Component, ViewChildren, AfterViewInit, QueryList } from '@angular/core';

import { HelloComponent } from './hello.component';

@Component({
selector: 'my-app',
templateUrl: './app.component.html',
styleUrls: [ './app.component.css' ]
})
export class AppComponent implements AfterViewInit {
name = 'Angular';
@ViewChildren(HelloComponent) hellos: QueryList<any>;

ngAfterViewInit() {

 this.hellos.forEach(hello =&gt; console.log(hello));

}
}
</pre>

You should this output in the console:

Now, let's explain the code.

First we import ViewChildrenAfterViewInit and QueryList from @angular/core package.

Next, we create a vquery configuration for accessing multiple DOM elements:

<pre class="ql-syntax" spellcheck="false">@ViewChildren(HelloComponent) hellos: QueryList<any>;
</pre>

@ViewChildren returns a QueryList which stores a list of items. When the state changes Angular will automatically update this query list.

Finally, in the ngAfterViewInit() method, we can iterate over the query list and log each DOM element:

<pre class="ql-syntax" spellcheck="false"> ngAfterViewInit() {
this.hellos.forEach(hello => console.log(hello));
}
</pre>

You can find the live example from this link.

Conclusions

In this tutorial, we've seen how we can access and modify the DOM in Angular 8 using ViewChild and ViewChildren decorators and a couple of other APIs like QueryList and ngAfterViewInit()


Originally published at techiediaries.com

==========================================

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☞ Angular & NodeJS - The MEAN Stack Guide

Angular 7 CRUD with Nodejs and MySQL Example

Angular 7 CRUD with Nodejs and MySQL Example

<span class="ql-cursor"></span>Below are the requirements for creating the CRUD on MEAN

  • Node.js
  • Angular CLI
  • Angular 7
  • Mysql
  • IDE or Text Editor

We assume that you have already available the above tools/frameworks and you are familiar with all the above that what individually actually does.

So now we will proceed step by step to achieve the task.

1. Update Angular CLI and Create Angular 7 Application

At first, We have to update the Angular CLI to the latest version. Open the terminal then go to the project folder and then type the below command to update the Angular CLI

<pre class="ql-syntax" spellcheck="false">sudo npm install -g @angular/cli </pre>

Once the above task finishes, Next task is to create new angular application with below command. So go to your project folder and then type below command:

<pre class="ql-syntax" spellcheck="false">ng new angular7-crud </pre>

then go to the newly created folder of angular application with **cd /angular7-crud ** and type **ng serve. **Now, open the browser then go to <a href="http://localhost:4200" title="" target="_blank">http://localhost:4200</a> you should see this page.

2. Create a server with node.js express and Mysql for REST APIs

create a separate folder named server for server-side stuff, Then move inside folder and create server.js by typing touch server.js

Let’s have a look on the server.js file

<pre class="ql-syntax" spellcheck="false">let app = require('express')(), server = require('http').Server(app), bodyParser = require('body-parser') express = require('express'), cors = require('cors'), http = require('http'), path = require('path');   let articleRoute = require('./Routes/article'), util = require('./Utilities/util');   app.use(bodyParser.json()); app.use(bodyParser.urlencoded({extended: false }));   app.use(cors());   app.use(function(err, req, res, next) { return res.send({ "statusCode": util.statusCode.ONE, "statusMessage":util.statusMessage.SOMETHING_WENT_WRONG }); });   app.use('/article', articleRoute);   // catch 404 and forward to error handler app.use(function(req, res, next) { next(); });   /*first API to check if server is running*/ app.get('*', (req, res) => { res.sendFile(path.join(__dirname, '../server/client/dist/index.html')); })     server.listen(3000,function(){ console.log('app listening on port: 3000'); }); </pre>

In the above file we can see, at the top, there are required packages for the app. Below that body parsing, middleware and routing is done.

The next task is to create routes and create a file article.js . So creating a folder name ‘Routes’ and adding article.js within it.

Add the below code for routing in article.js inside routing folder

<pre class="ql-syntax" spellcheck="false">let express = require('express'), router = express.Router(), util = require('../Utilities/util'), articleService = require('../Services/article');   /**Api to create article */ router.post('/create-article', (req, res) => { articleService.createArticle(req.body, (data) => { res.send(data); }); });   // /**Api to update article */ router.put('/update-article', (req, res) => { articleService.updateArticle(req.body, (data) => { res.send(data); }); });   // /**Api to delete the article */ router.delete('/delete-article', (req, res) => { articleService.deleteArticle(req.query, (data) => { res.send(data); }); });   /**Api to get the list of article */ router.get('/get-article', (req, res) => { documentService.getArticle(req.query, (data) => { res.send(data); }); });   // /**API to get the article by id... */ router.get('/get-article-by-id', (req, res) => { articleService.getArticleById(req.query, (data) => { res.send(data); }); });   module.exports = router; </pre>


Now create a folder named Utilities for all config, common methods and mysql connection config.

Now I am adding config values in a file named config.js

<pre class="ql-syntax" spellcheck="false">let environment = "dev";   let serverURLs = { "dev": { "NODE_SERVER": "http://localhost", "NODE_SERVER_PORT": "3000", "MYSQL_HOST": 'localhost', "MYSQL_USER": 'root', "MYSQL_PASSWORD": 'password', 'MYSQL_DATABASE': 'demo_angular7_crud', } }   let config = { "DB_URL_MYSQL": { "host": `${serverURLs[environment].MYSQL_HOST}`, "user": `${serverURLs[environment].MYSQL_USER}`, "password": `${serverURLs[environment].MYSQL_PASSWORD}`, "database": `${serverURLs[environment].MYSQL_DATABASE}` }, "NODE_SERVER_PORT": { "port": `${serverURLs[environment].NODE_SERVER_PORT}` }, "NODE_SERVER_URL": { "url": `${serverURLs[environment].NODE_SERVER}` } };   module.exports = { config: config }; </pre>

Now configure mysql connection. So I am writing the connection with database in a separate file. So creating a file named mysqkConfig.js under Utilities folder and adding the below line of code for mysql connection:

 

<pre class="ql-syntax" spellcheck="false">var config = require("../Utilities/config").config; var mysql = require('mysql'); var connection = mysql.createConnection({ host: config.DB_URL_MYSQL.host, user: config.DB_URL_MYSQL.user, password: config.DB_URL_MYSQL.password, database: config.DB_URL_MYSQL.database, });   connection.connect(() => { require('../Models/Article').initialize(); });   let getDB = () => { return connection; }   module.exports = { getDB: getDB } </pre>

Now I am creating separate file name util.js to save common methods and common status code/message:

<pre class="ql-syntax" spellcheck="false">// Define Error Codes let statusCode = { OK: 200, FOUR_ZERO_FOUR: 404, FOUR_ZERO_THREE: 403, FOUR_ZERO_ONE: 401, FIVE_ZERO_ZERO: 500 };   // Define Error Messages let statusMessage = { SERVER_BUSY : 'Our Servers are busy. Please try again later.', DATA_UPDATED: 'Data updated successfully.', DELETE_DATA : 'Delete data successfully',   };   module.exports = { statusCode: statusCode, statusMessage: statusMessage } </pre>

Now the next part is model, So create a folder named Models and create a file Article.js and add the below code in it:

<pre class="ql-syntax" spellcheck="false">let mysqlConfig = require("../Utilities/mysqlConfig");   let initialize = () => { mysqlConfig.getDB().query("create table IF NOT EXISTS article (id INT auto_increment primary key, category VARCHAR(30), title VARCHAR(24))");   }   module.exports = { initialize: initialize } </pre>

Now create DAO folder and add a file articleDAO.js for writting the mysql queries common functions:

<pre class="ql-syntax" spellcheck="false">let dbConfig = require("../Utilities/mysqlConfig");

 
let getArticle = (criteria, callback) => {
//criteria.aricle_id ? conditions += and aricle_id = '${criteria.aricle_id}' : true;
dbConfig.getDB().query(select * from article where 1,criteria, callback);
}
 
let getArticleDetail = (criteria, callback) => {
    let conditions = "";
criteria.id ? conditions +=  and id = '${criteria.id}' : true;
dbConfig.getDB().query(select * from article where 1&nbsp;${conditions}, callback);
}
 
let createArticle = (dataToSet, callback) => {
console.log("insert into article set ? ", dataToSet,'pankaj')
dbConfig.getDB().query("insert into article set ? ", dataToSet, callback);
}
 
let deleteArticle = (criteria, callback) => {
let conditions = "";
criteria.id ? conditions +=  and id = '${criteria.id}' : true;
console.log(delete from article where 1&nbsp;${conditions});
dbConfig.getDB().query(delete from article where 1&nbsp;${conditions}, callback);
 
}
 
let updateArticle = (criteria,dataToSet,callback) => {
    let conditions = "";
let setData = "";
criteria.id ? conditions +=  and id = '${criteria.id}' : true;
dataToSet.category ? setData += category = '${dataToSet.category}' : true;
dataToSet.title ? setData += , title = '${dataToSet.title}' : true;
console.log(UPDATE article SET&nbsp;${setData}&nbsp;where 1&nbsp;${conditions});
dbConfig.getDB().query(UPDATE article SET&nbsp;${setData}&nbsp;where 1&nbsp;${conditions}, callback);
}
module.exports = {
getArticle : getArticle,
createArticle : createArticle,
deleteArticle : deleteArticle,
updateArticle : updateArticle,
getArticleDetail : getArticleDetail
}
</pre>

Now one create Services folder and add a file article.js for all the logic of API

<pre class="ql-syntax" spellcheck="false"> let async = require('async'),
parseString = require('xml2js').parseString;
 
let util = require('../Utilities/util'),
articleDAO = require('../DAO/articleDAO');
//config = require("../Utilities/config").config;
 
 
/**API to create the atricle */
let createArticle = (data, callback) => {
async.auto({
article: (cb) => {
var dataToSet = {
"category":data.category?data.category:'',
"title":data.title,
}
console.log(dataToSet);
articleDAO.createArticle(dataToSet, (err, dbData) => {
if (err) {
cb(null, { "statusCode": util.statusCode.FOUR_ZERO_ONE, "statusMessage":util.statusMessage.SERVER_BUSY });
return;
}
 
cb(null, { "statusCode": util.statusCode.OK, "statusMessage":util.statusMessage.DATA_UPDATED,"result":dataToSet });
});
}
//]
}, (err, response) => {
callback(response.article);
});
}
 
/**API to update the article */
let updateArticle = (data,callback) => {
async.auto({
articleUpdate :(cb) =>{
if (!data.id) {
cb(null, { "statusCode": util.statusCode.FOUR_ZERO_ONE, "statusMessage":util.statusMessage.PARAMS_MISSING })
return;
}
console.log('phase 1');
var criteria = {
id : data.id,
}
var dataToSet={
"category": data.category,
"title":data.title,
}
console.log(criteria,'test',dataToSet);
                    articleDAO.updateArticle(criteria, dataToSet, (err, dbData)=>{
                        if(err){
cb(null,{"statusCode":util.statusCode.FOUR_ZERO_ONE,"statusMessage":util.statusMessage.SERVER_BUSY});
                        return; 
                        }
                        else{
cb(null, { "statusCode": util.statusCode.OK, "statusMessage":util.statusMessage.DATA_UPDATED,"result":dataToSet });                        
                        }
                    });
}
}, (err,response) => {
callback(response.articleUpdate);
});
}
 
/**API to delete the subject */
let deleteArticle = (data,callback) => {
console.log(data,'data to set')
async.auto({
removeArticle :(cb) =>{
if (!data.id) {
cb(null, { "statusCode": util.statusCode.FOUR_ZERO_ONE, "statusMessage":util.statusMessage.PARAMS_MISSING })
return;
}
var criteria = {
id : data.id,
}
articleDAO.deleteArticle(criteria,(err,dbData) => {
if (err) {
console.log(err);
cb(null, { "statusCode": util.statusCode.FOUR_ZERO_ONE, "statusMessage":util.statusMessage.SERVER_BUSY });
return;
}
cb(null, { "statusCode": util.statusCode.OK, "statusMessage": util.statusMessage.DELETE_DATA });
});
}
}, (err,response) => {
callback(response.removeArticle);
});
}
 
/***API to get the article list */
let getArticle = (data, callback) => {
async.auto({
article: (cb) => {
articleDAO.getArticle({},(err, data) => {
if (err) {
cb(null, {"errorCode": util.statusCode.INTERNAL_SERVER_ERROR,"statusMessage":util.statusMessage.SERVER_BUSY});
return;
}
cb(null, data);
return;
});
}
}, (err, response) => {
callback(response.article);
})
}
 
/***API to get the article detail by id */
let getArticleById = (data, callback) => {
async.auto({
article: (cb) => {
let criteria = {
"id":data.id
}
articleDAO.getArticleDetail(criteria,(err, data) => {
if (err) {
console.log(err,'error----');
cb(null, {"errorCode": util.statusCode.INTERNAL_SERVER_ERROR,"statusMessage":util.statusMessage.SERVER_BUSY});
return;
}
cb(null, data[0]);
return;
});
}
}, (err, response) => {
callback(response.article);
})
}
 
module.exports = {
createArticle : createArticle,
updateArticle : updateArticle,
deleteArticle : deleteArticle,
getArticle : getArticle,
getArticleById : getArticleById
};
</pre>

3. Create angular component for performing CRUD task of article

<pre class="ql-syntax" spellcheck="false">ng g component article
</pre>

Above command will generate all required files for build article component and also automatically added this component to app.module.ts.

<pre class="ql-syntax" spellcheck="false">create src/app/article/article.component.css (0 bytes)
create src/app/article/article.component.html (23 bytes)
create src/app/article/article.component.spec.ts (614 bytes)
create src/app/article/article.component.ts (321 bytes)
update src/app/app.module.ts (390 bytes)
</pre>

Now we need to add HttpClientModule to app.module.ts. Open and edit src/app/app.module.ts then add this import. And add it to @NgModule imports after BrowserModule. Now our app.module.ts will have following code:

<pre class="ql-syntax" spellcheck="false"> import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { ReactiveFormsModule } from '@angular/forms';
import { HttpModule } from '@angular/http';
 
import { AppComponent } from './app.component';
import { ArticleComponent } from './article.component';
import { ArticleService } from './article.service';
 
@NgModule({
imports: [
BrowserModule,
HttpModule,
ReactiveFormsModule
],
declarations: [
AppComponent,
ArticleComponent
],
providers: [
ArticleService
],
bootstrap: [
AppComponent
]
})
export class AppModule { }
</pre>

Now create a service file where we will make all the request to the server for CRUD operation. Command for creating service is ng g service artcle , for now I have just created a file named it article.service.ts. Let's have a look in the code inside this file.

<pre class="ql-syntax" spellcheck="false">import { Injectable } from '@angular/core';
import { Http, Response, Headers, URLSearchParams, RequestOptions } from '@angular/http';
import { Observable } from 'rxjs';
import 'rxjs/add/operator/map';
import 'rxjs/add/operator/catch';
 
import { Article } from './article';
 
@Injectable()
export class ArticleService {
//URL for CRUD operations
    articleUrl = "http://localhost:3000/article";
    //Create constructor to get Http instance
    constructor(private http:Http) {
    }
    
    //Fetch all articles
getAllArticles(): Observable<Article[]> {
return this.http.get(this.articleUrl+"/get-article")
              .map(this.extractData)
         .catch(this.handleError);
 
}
    //Create article
createArticle(article: Article):Observable<number> {
     let cpHeaders = new Headers({ 'Content-Type': 'application/json' });
let options = new RequestOptions({ headers: cpHeaders });
return this.http.post(this.articleUrl+"/create-article", article, options)
.map(success => success.status)
.catch(this.handleError);
}
    //Fetch article by id
getArticleById(articleId: string): Observable<Article> {
        let cpHeaders = new Headers({ 'Content-Type': 'application/json' });
        let options = new RequestOptions({ headers: cpHeaders });
        console.log(this.articleUrl +"/get-article-by-id?id="+ articleId);
        return this.http.get(this.articleUrl +"/get-article-by-id?id="+ articleId)
             .map(this.extractData)
             .catch(this.handleError);
}   
    //Update article
updateArticle(article: Article):Observable<number> {
     let cpHeaders = new Headers({ 'Content-Type': 'application/json' });
        let options = new RequestOptions({ headers: cpHeaders });
return this.http.put(this.articleUrl +"/update-article", article, options)
.map(success => success.status)
.catch(this.handleError);
}
//Delete article    
deleteArticleById(articleId: string): Observable<number> {
        let cpHeaders = new Headers({ 'Content-Type': 'application/json' });
        let options = new RequestOptions({ headers: cpHeaders });
        return this.http.delete(this.articleUrl +"/delete-article?id="+ articleId)
             .map(success => success.status)
             .catch(this.handleError);
}   
    private extractData(res: Response) {
        let body = res.json();
return body;
}
private handleError (error: Response | any) {
        console.error(error.message || error);
        return Observable.throw(error.status);
}
}
</pre>

In the above file we have made all the http request for the CRUD operation. Observables of rxjs library has been used to handle the data fetching from http request.

 

Now let's move to the next file, article.component.ts. Here we have all the login part of the app. Let's have a look code inside this file:

<pre class="ql-syntax" spellcheck="false">import { Component, OnInit } from '@angular/core';
import { FormControl, FormGroup, Validators } from '@angular/forms';
 
import { ArticleService } from './article.service';
import { Article } from './article';
 
@Component({
selector: 'app-article',
templateUrl: './article.component.html',
styleUrls: ['./article.component.css']
})
export class ArticleComponent implements OnInit {
//Component properties
allArticles: Article[];
statusCode: number;
requestProcessing = false;
articleIdToUpdate = null;
processValidation = false;
//Create form
articleForm = new FormGroup({
title: new FormControl('', Validators.required),
category: new FormControl('', Validators.required)   
});
//Create constructor to get service instance
constructor(private articleService: ArticleService) {
}
//Create ngOnInit() and and load articles
ngOnInit(): void {
     this.getAllArticles();
}
//Fetch all articles
 
getAllArticles() {
        this.articleService.getAllArticles()
         .subscribe(
data => this.allArticles = data,
                errorCode => this.statusCode = errorCode);
                
}
//Handle create and update article
onArticleFormSubmit() {
     this.processValidation = true;
     if (this.articleForm.invalid) {
     return; //Validation failed, exit from method.
     }
     //Form is valid, now perform create or update
this.preProcessConfigurations();
     let article = this.articleForm.value;
     if (this.articleIdToUpdate === null) {
     //Generate article id then create article
this.articleService.getAllArticles()
     .subscribe(articles => {
            
         //Generate article id    
         let maxIndex = articles.length - 1;
         let articleWithMaxIndex = articles[maxIndex];
         let articleId = articleWithMaxIndex.id + 1;
         article.id = articleId;
         console.log(article,'this is form data---');
         //Create article
    this.articleService.createArticle(article)
             .subscribe(successCode => {
                    this.statusCode = successCode;
                    this.getAllArticles();  
                    this.backToCreateArticle();
                 },
                 errorCode => this.statusCode = errorCode
             );
         });        
     } else {
  //Handle update article
article.id = this.articleIdToUpdate;        
     this.articleService.updateArticle(article)
     .subscribe(successCode => {
         this.statusCode = successCode;
                 this.getAllArticles();  
                    this.backToCreateArticle();
             },
         errorCode => this.statusCode = errorCode);  
     }
}
//Load article by id to edit
loadArticleToEdit(articleId: string) {
this.preProcessConfigurations();
this.articleService.getArticleById(articleId)
     .subscribe(article => {
            console.log(article,'poiuytre');
         this.articleIdToUpdate = article.id;
                    this.articleForm.setValue({ title: article.title, category: article.category });
                    this.processValidation = true;
                    this.requestProcessing = false;
         },
         errorCode => this.statusCode = errorCode);
}
//Delete article
deleteArticle(articleId: string) {
this.preProcessConfigurations();
this.articleService.deleteArticleById(articleId)
     .subscribe(successCode => {
         //this.statusCode = successCode;
                    //Expecting success code 204 from server
                    this.statusCode = 204;
                 this.getAllArticles();  
                 this.backToCreateArticle();
             },
         errorCode => this.statusCode = errorCode);
}
//Perform preliminary processing configurations
preProcessConfigurations() {
this.statusCode = null;
     this.requestProcessing = true;
}
//Go back from update to create
backToCreateArticle() {
this.articleIdToUpdate = null;
this.articleForm.reset(); 
     this.processValidation = false;
}
}
</pre>

Now we have to show the task over browser, So lets have a look inside article.component.html file.

<pre class="ql-syntax" spellcheck="false"><h1 class="text-center">Angular 7 CRUD Demo App</h1>
<h3 class="text-center" *ngIf="articleIdToUpdate; else create">
Update Article for Id: {{articleIdToUpdate}}
</h3>
<ng-template #create>
<h3 class="text-center"> Create New Article </h3>
</ng-template>
<div>
<form [formGroup]="articleForm" (ngSubmit)="onArticleFormSubmit()">
<table class="table-striped" style="margin:0 auto;">
<tr><td>Enter Title</td><td><input formControlName="title">
   <label *ngIf="articleForm.get('title').invalid && processValidation" [ngClass] = "'error'"> Title is required. </label>
 </td></tr>
<tr><td>Enter Category</td><td><input formControlName="category">
   <label *ngIf="articleForm.get('category').invalid && processValidation" [ngClass] = "'error'">Category is required. </label>
  </td></tr>  
<tr><td colspan="2">
   <button class="btn btn-default" *ngIf="!articleIdToUpdate">CREATE</button>
    <button class="btn btn-default" *ngIf="articleIdToUpdate">UPDATE</button>
   <button (click)="backToCreateArticle()" *ngIf="articleIdToUpdate">Go Back</button>
  </td></tr>
</table>
</form>
<br/>
<div class="text-center" *ngIf="statusCode; else processing">
<div *ngIf="statusCode === 201" [ngClass] = "'success'">
   Article added successfully.
</div>
<div *ngIf="statusCode === 409" [ngClass] = "'success'">
Article already exists.
</div>   
<div *ngIf="statusCode === 200" [ngClass] = "'success'">
Article updated successfully.
</div>   
<div *ngIf="statusCode === 204" [ngClass] = "'success'">
Article deleted successfully.
</div>   
<div *ngIf="statusCode === 500" [ngClass] = "'error'">
Internal Server Error.
</div> 
</div>
<ng-template #processing>
  <img *ngIf="requestProcessing" src="assets/images/loading.gif">
</ng-template>
</div>
<h3 class="text-center">Article List</h3>
<table class="table-striped" style="margin:0 auto;" *ngIf="allArticles">
<tr><th> Id</th> <th>Title</th><th>Category</th><th></th><th></th></tr>
<tr *ngFor="let article of allArticles" >
<td>{{article.id}}</td> <td>{{article.title}}</td> <td>{{article.category}}</td>
  <td><button class="btn btn-default" type="button"(click)="loadArticleToEdit(article.id)">Edit</button> </td>
  <td><button class="btn btn-default" type="button"(click)="deleteArticle(article.id)">Delete</button></td>
</tr>
</table>
</pre>

Now since I have created server and client two separate folder for nodejs and angular task. So will run both the apps with npm start over two tabs of terminal.

On the browser, over link <a href="http://localhost:4200." target="_blank">http://localhost:4200.</a> App will look like below

 

That’s all for now. Thank you for reading and I hope this post will be very helpful for creating CRUD operations with angular7,node.js & mysql.



================================================

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Learn More

☞ <a href="https://l.morioh.com/b0a3f595aa?r=http://learnstartup.net/p/H1jE_tD3l" title="" target="_blank">Angular 8 (formerly Angular 2) - The Complete Guide</a>

☞ <a href="https://l.morioh.com/b0a3f595aa?r=http://learnstartup.net/p/HJigQzgZx" title="" target="_blank">Learn and Understand AngularJS</a>

☞ <a href="https://l.morioh.com/b0a3f595aa?r=http://learnstartup.net/p/ry7Ey9yKW" title="" target="_blank">The Complete Angular Course: Beginner to Advanced</a>

☞ <a href="https://l.morioh.com/b0a3f595aa?r=http://learnstartup.net/p/rkjpGfa5W" title="" target="_blank">Angular Crash Course for Busy Developers</a>

☞ <a href="https://l.morioh.com/b0a3f595aa?r=http://learnstartup.net/p/SkdU19JFZ" title="" target="_blank">Angular Essentials (Angular 2+ with TypeScript)</a>

☞ <a href="https://l.morioh.com/b0a3f595aa?r=http://learnstartup.net/p/B1oHaY8cM" title="" target="_blank">Angular (Full App) with Angular Material, Angularfire & NgRx</a>

☞ <a href="https://l.morioh.com/b0a3f595aa?r=http://learnstartup.net/p/Skf7ILFw3l" title="" target="_blank">Angular & NodeJS - The MEAN Stack Guide</a>



Angular 8 Forms Tutorial - Reactive Forms Validation Example

Angular 8 Forms Tutorial - Reactive Forms Validation Example

The example is a simple registration form with pretty standard fields for title, first name, last name, email, password, confirm password and an accept Ts & Cs checkbox. All fields are required including the checkbox, the email field must be a valid email address and the password field must have a min length of 6. There's also a custom validator called MustMatch which is used to validate that the confirm password and password fields match.

I've setup the form to validate on submit rather than as soon as each field is changed, this is implemented with a submitted property in the app component that is set to true when the form is submitted for the first time, and reset to false if the cancel button is clicked.

Styling of the example is all done with Bootstrap 4.3 CSS.

See on StackBlitz at https://stackblitz.com/edit/angular-8-reactive-form-validation

Reactive Forms Validation App Component

The app component defines the form fields and validators for our registration form using an Angular FormBuilder to create an instance of a FormGroup that is stored in the registerForm property. The registerForm is then bound to the form in the app template below using the [formGroup] directive.

I also added a getter f as a convenience property to make it easier to access form controls from the template. So for example you can access the confirmPassword field in the template using f.confirmPassword instead of registerForm.controls.confirmPassword.

import { Component, OnInit } from '@angular/core';
import { FormBuilder, FormGroup, Validators } from '@angular/forms';

// import custom validator to validate that password and confirm password fields match
import { MustMatch } from './_helpers/must-match.validator';

@Component({ selector: 'app', templateUrl: 'app.component.html' })
export class AppComponent implements OnInit {
    registerForm: FormGroup;
    submitted = false;

    constructor(private formBuilder: FormBuilder) { }

    ngOnInit() {
        this.registerForm = this.formBuilder.group({
            title: ['', Validators.required],
            firstName: ['', Validators.required],
            lastName: ['', Validators.required],
            email: ['', [Validators.required, Validators.email]],
            password: ['', [Validators.required, Validators.minLength(6)]],
            confirmPassword: ['', Validators.required],
            acceptTerms: [false, Validators.requiredTrue]
        }, {
            validator: MustMatch('password', 'confirmPassword')
        });
    }

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

    onSubmit() {
        this.submitted = true;

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

        // display form values on success
        alert('SUCCESS!! :-)\n\n' + JSON.stringify(this.registerForm.value, null, 4));
    }

    onReset() {
        this.submitted = false;
        this.registerForm.reset();
    }
}

Reactive Forms Validation App Template

The app component template contains all the html markup for displaying the example registration form in your browser. The form element uses the [formGroup] directive to bind to the registerForm FormGroup in the app component above.

The form binds the form submit event to the onSubmit() handler in the app component using the Angular event binding (ngSubmit)="onSubmit()". Validation messages are displayed only after the user attempts to submit the form for the first time, this is controlled with the submitted property of the app component.

The cancel button click event is bound to the onReset() handler in the app component using the Angular event binding (click)="onReset()".

<!-- main app container -->
<div class="card m-3">
    <h5 class="card-header">Angular 8 Reactive Form Validation</h5>
    <div class="card-body">
        <form [formGroup]="registerForm" (ngSubmit)="onSubmit()">
            <div class="form-row">
                <div class="form-group col">
                    <label>Title</label>
                    <select formControlName="title" class="form-control" [ngClass]="{ 'is-invalid': submitted && f.title.errors }">
                        <option value=""></option>
                        <option value="Mr">Mr</option>
                        <option value="Mrs">Mrs</option>
                        <option value="Miss">Miss</option>
                        <option value="Ms">Ms</option>
                    </select>
                    <div *ngIf="submitted && f.title.errors" class="invalid-feedback">
                        <div *ngIf="f.title.errors.required">Title is required</div>
                    </div>
                </div>
                <div class="form-group col-5">
                    <label>First Name</label>
                    <input type="text" formControlName="firstName" class="form-control" [ngClass]="{ 'is-invalid': submitted && f.firstName.errors }" />
                    <div *ngIf="submitted && f.firstName.errors" class="invalid-feedback">
                        <div *ngIf="f.firstName.errors.required">First Name is required</div>
                    </div>
                </div>
                <div class="form-group col-5">
                    <label>Last Name</label>
                    <input type="text" formControlName="lastName" class="form-control" [ngClass]="{ 'is-invalid': submitted && f.lastName.errors }" />
                    <div *ngIf="submitted && f.lastName.errors" class="invalid-feedback">
                        <div *ngIf="f.lastName.errors.required">Last Name is required</div>
                    </div>
                </div>
            </div>
            <div class="form-group">
                <label>Email</label>
                <input type="text" formControlName="email" class="form-control" [ngClass]="{ 'is-invalid': submitted && f.email.errors }" />
                <div *ngIf="submitted && f.email.errors" class="invalid-feedback">
                    <div *ngIf="f.email.errors.required">Email is required</div>
                    <div *ngIf="f.email.errors.email">Email must be a valid email address</div>
                </div>
            </div>
            <div class="form-row">
                <div class="form-group col">
                    <label>Password</label>
                    <input type="password" formControlName="password" class="form-control" [ngClass]="{ 'is-invalid': submitted && f.password.errors }" />
                    <div *ngIf="submitted && f.password.errors" class="invalid-feedback">
                        <div *ngIf="f.password.errors.required">Password is required</div>
                        <div *ngIf="f.password.errors.minlength">Password must be at least 6 characters</div>
                    </div>
                </div>
                <div class="form-group col">
                    <label>Confirm Password</label>
                    <input type="password" formControlName="confirmPassword" class="form-control" [ngClass]="{ 'is-invalid': submitted && f.confirmPassword.errors }" />
                    <div *ngIf="submitted && f.confirmPassword.errors" class="invalid-feedback">
                        <div *ngIf="f.confirmPassword.errors.required">Confirm Password is required</div>
                        <div *ngIf="f.confirmPassword.errors.mustMatch">Passwords must match</div>
                    </div>
                </div>
            </div>
            <div class="form-group form-check">
                <input type="checkbox" formControlName="acceptTerms" id="acceptTerms" class="form-check-input" [ngClass]="{ 'is-invalid': submitted && f.acceptTerms.errors }" />
                <label for="acceptTerms" class="form-check-label">Accept Terms & Conditions</label>
                <div *ngIf="submitted && f.acceptTerms.errors" class="invalid-feedback">Accept Ts & Cs is required</div>
            </div>
            <div class="text-center">
                <button class="btn btn-primary mr-1">Register</button>
                <button class="btn btn-secondary" type="reset" (click)="onReset()">Cancel</button>
            </div>
        </form>
    </div>
</div>

Reactive Forms Custom "Must Match" Validator

The custom MustMatch validator is used in this example to validate that both of the password fields - password and confirmPassword - are matching. However it can be used to validate that any pair of fields is matching (e.g. email and confirm email fields).

It works slightly differently than a typical custom validator because I'm setting the error on the second field instead of returning it to be set on the formGroup. I did it this way because I think it makes the template a bit cleaner and more intuitive, the mustMatch validation error is displayed below the confirmPassword field so I think it makes sense that the error is attached the the confirmPassword form control.

import { FormGroup } from '@angular/forms';

// custom validator to check that two fields match
export function MustMatch(controlName: string, matchingControlName: string) {
    return (formGroup: FormGroup) => {
        const control = formGroup.controls[controlName];
        const matchingControl = formGroup.controls[matchingControlName];

        if (matchingControl.errors && !matchingControl.errors.mustMatch) {
            // return if another validator has already found an error on the matchingControl
            return;
        }

        // set error on matchingControl if validation fails
        if (control.value !== matchingControl.value) {
            matchingControl.setErrors({ mustMatch: true });
        } else {
            matchingControl.setErrors(null);
        }
    }
}

Reactive Forms Validation App Module

There isn't much going on in the app module other than the standard stuff, the main thing you need to remember for using reactive forms in Angular is to import the ReactiveFormsModule from '@angular/forms' and include it in the imports array of the @NgModule decorator.

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

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

@NgModule({
    imports: [
        BrowserModule,
        ReactiveFormsModule
    ],
    declarations: [
        AppComponent
    ],
    bootstrap: [AppComponent]
})
export class AppModule { }

Thanks for reading

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Further reading

Angular 8 (formerly Angular 2) - The Complete Guide

Angular & NodeJS - The MEAN Stack Guide

The Web Developer Bootcamp

Angular 8 is coming

MEAN Stack Angular 8 CRUD Web Application

Angular 8 + Spring Boot 2.2: Build a CRUD App Today!

Best 17 Angular Libraries Every Angular Developers Should Know in 2019

React vs Angular vs Vue.js by Example

Best JavaScript Frameworks, Libraries and Tools to Use in 2019

Angular Authentication with JWT 

Build RESTful API In Laravel 5.8 Example

Build RESTful API In Laravel 5.8 Example


If you want to create web services with php than i will must suggest to use laravel 5.8 to create apis because laravel provide structure with authentication using passport. Based on structure it will become a very easily way to create rest apis.

Just Few days ago, laravel released it's new version as laravel 5.8. As we know laravel is a more popular because of security feature. So many of the developer choose laravel to create rest api for mobile app developing. Yes Web services is a very important when you create web and mobile developing, because you can create same database and work with same data.

Follow bellow few steps to create restful api example in laravel 5.8 app.

Step 1: Download Laravel 5.8

I am going to explain step by step from scratch so, we need to get fresh Laravel 5.8 application using bellow command, So open your terminal OR command prompt and run bellow command:

<pre class="ql-syntax" spellcheck="false">composer create-project --prefer-dist laravel/laravel blog </pre>

Step 2: Install Passport

In this step we need to install passport via the Composer package manager, so one your terminal and fire bellow command:

<pre class="ql-syntax" spellcheck="false">composer require laravel/passport </pre>

After successfully install package, we require to get default migration for create new passport tables in our database. so let's run bellow command.

<pre class="ql-syntax" spellcheck="false">php artisan migrate </pre>

Next, we need to install passport using command, Using passport:install command, it will create token keys for security. So let's run bellow command:

<pre class="ql-syntax" spellcheck="false">php artisan passport:install </pre>

Step 3: Passport Configuration

In this step, we have to configuration on three place model, service provider and auth config file. So you have to just following change on that file.

In model we added HasApiTokens class of Passport,

In AuthServiceProvider we added "Passport::routes()",

In auth.php, we added api auth configuration.

app/User.php

<pre class="ql-syntax" spellcheck="false"><?php

namespace App;

use Illuminate\Notifications\Notifiable;
use Illuminate\Contracts\Auth\MustVerifyEmail;
use Laravel\Passport\HasApiTokens;
use Illuminate\Foundation\Auth\User as Authenticatable;

class User extends Authenticatable implements MustVerifyEmail
{
use HasApiTokens, Notifiable;

/**
 * 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',
];

}
</pre>

app/Providers/AuthServiceProvider.php

<pre class="ql-syntax" spellcheck="false"><?php

namespace App\Providers;

use Laravel\Passport\Passport;
use Illuminate\Support\Facades\Gate;
use Illuminate\Foundation\Support\Providers\AuthServiceProvider as ServiceProvider;

class AuthServiceProvider extends ServiceProvider
{
/**
* The policy mappings for the application.
*
* @var array
*/
protected $policies = [
'App\Model' => 'App\Policies\ModelPolicy',
];

/**
 * Register any authentication / authorization services.
 *
 * @return void
 */
public function boot()
{
    $this-&gt;registerPolicies();

    Passport::routes();
}

}
</pre>

config/auth.php

<pre class="ql-syntax" spellcheck="false"><?php

return [
.....
'guards' => [
'web' => [
'driver' => 'session',
'provider' => 'users',
],
'api' => [
'driver' => 'passport',
'provider' => 'users',
],
],
.....
]
</pre>

Step 4: Add Product Table and Model

next, we require to create migration for posts table using Laravel 5.8 php artisan command, so first fire bellow command:

<pre class="ql-syntax" spellcheck="false">php artisan make:migration create_products_table
</pre>

After this command you will find one file in following path database/migrations and you have to put bellow code in your migration file for create products table.

<pre class="ql-syntax" spellcheck="false"><?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->increments('id');
$table->string('name');
$table->text('detail');
$table->timestamps();
});
}

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

}
</pre>

After create migration we need to run above migration by following command:

<pre class="ql-syntax" spellcheck="false">php artisan migrate
</pre>

After create "products" table you should create Product model for products, so first create file in this path app/Product.php and put bellow content in item.php file:


app/Product.php

<pre class="ql-syntax" spellcheck="false"><?php

namespace App;

use Illuminate\Database\Eloquent\Model;

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

Step 5: Create API Routes

In this step, we will create api routes. Laravel provide api.php file for write web services route. So, let's add new route on that file.

routes/api.php

<pre class="ql-syntax" spellcheck="false"><?php

/*
|--------------------------------------------------------------------------

API Routes
Here is where you can register API routes for your application. These
routes are loaded by the RouteServiceProvider within a group which
is assigned the "api" middleware group. Enjoy building your API!

*/

Route::post('register', 'API\[email protected]');

Route::middleware('auth:api')->group( function () {
Route::resource('products', 'API\ProductController');
});
</pre>

Step 6: Create Controller Files

in next step, now we have create new controller as BaseController, ProductController and RegisterController, i created new folder "API" in Controllers folder because we will make alone APIs controller, So let's create both controller:

app/Http/Controllers/API/BaseController.php

<pre class="ql-syntax" spellcheck="false"><?php

namespace App\Http\Controllers\API;

use Illuminate\Http\Request;
use App\Http\Controllers\Controller as Controller;

class BaseController extends Controller
{
/**
* success response method.
*
* @return \Illuminate\Http\Response
*/
public function sendResponse($result, $message)
{
$response = [
'success' => true,
'data' => $result,
'message' => $message,
];

    return response()-&gt;json($response, 200);
}

/**
 * return error response.
 *
 * @return \Illuminate\Http\Response
 */
public function sendError($error, $errorMessages = [], $code = 404)
{
	$response = [
        'success' =&gt; false,
        'message' =&gt; $error,
    ];

    if(!empty($errorMessages)){
        $response['data'] = $errorMessages;
    }

    return response()-&gt;json($response, $code);
}

}
</pre>

app/Http/Controllers/API/ProductController.php

<pre class="ql-syntax" spellcheck="false"><?php

namespace App\Http\Controllers\API;

use Illuminate\Http\Request;
use App\Http\Controllers\API\BaseController as BaseController;
use App\Product;
use Validator;

class ProductController extends BaseController
{
/**
* Display a listing of the resource.
*
* @return \Illuminate\Http\Response
*/
public function index()
{
$products = Product::all();

    return $this-&gt;sendResponse($products-&gt;toArray(), 'Products retrieved successfully.');
}

/**
 * Store a newly created resource in storage.
 *
 * @param  \Illuminate\Http\Request  $request
 * @return \Illuminate\Http\Response
 */
public function store(Request $request)
{
    $input = $request-&gt;all();

    $validator = Validator::make($input, [
        'name' =&gt; 'required',
        'detail' =&gt; 'required'
    ]);

    if($validator-&gt;fails()){
        return $this-&gt;sendError('Validation Error.', $validator-&gt;errors());       
    }

    $product = Product::create($input);

    return $this-&gt;sendResponse($product-&gt;toArray(), 'Product created successfully.');
}

/**
 * Display the specified resource.
 *
 * @param  int  $id
 * @return \Illuminate\Http\Response
 */
public function show($id)
{
    $product = Product::find($id);

    if (is_null($product)) {
        return $this-&gt;sendError('Product not found.');
    }

    return $this-&gt;sendResponse($product-&gt;toArray(), 'Product retrieved successfully.');
}

/**
 * Update the specified resource in storage.
 *
 * @param  \Illuminate\Http\Request  $request
 * @param  int  $id
 * @return \Illuminate\Http\Response
 */
public function update(Request $request, Product $product)
{
    $input = $request-&gt;all();

    $validator = Validator::make($input, [
        'name' =&gt; 'required',
        'detail' =&gt; 'required'
    ]);

    if($validator-&gt;fails()){
        return $this-&gt;sendError('Validation Error.', $validator-&gt;errors());       
    }

    $product-&gt;name = $input['name'];
    $product-&gt;detail = $input['detail'];
    $product-&gt;save();

    return $this-&gt;sendResponse($product-&gt;toArray(), 'Product updated successfully.');
}

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

    return $this-&gt;sendResponse($product-&gt;toArray(), 'Product deleted successfully.');
}

}
</pre>

app/Http/Controllers/API/RegisterController.php

<pre class="ql-syntax" spellcheck="false"><?php

namespace App\Http\Controllers\API;

use Illuminate\Http\Request;
use App\Http\Controllers\API\BaseController as BaseController;
use App\User;
use Illuminate\Support\Facades\Auth;
use Validator;

class RegisterController extends BaseController
{
/**
* Register api
*
* @return \Illuminate\Http\Response
*/
public function register(Request $request)
{
$validator = Validator::make($request->all(), [
'name' => 'required',
'email' => 'required|email',
'password' => 'required',
'c_password' => 'required|same:password',
]);

    if($validator-&gt;fails()){
        return $this-&gt;sendError('Validation Error.', $validator-&gt;errors());       
    }

    $input = $request-&gt;all();
    $input['password'] = bcrypt($input['password']);
    $user = User::create($input);
    $success['token'] =  $user-&gt;createToken('MyApp')-&gt;accessToken;
    $success['name'] =  $user-&gt;name;

    return $this-&gt;sendResponse($success, 'User register successfully.');
}

}
</pre>

Now we are ready to to run full restful api and also passport api in laravel. so let's run our example so run bellow command for quick run:

<pre class="ql-syntax" spellcheck="false">php artisan serve
</pre>

make sure in details api we will use following headers as listed bellow:

<pre class="ql-syntax" spellcheck="false">'headers' => [
'Accept' => 'application/json',
'Authorization' => 'Bearer '.$accessToken,
]
</pre>

Here is Routes URL with Verb:

1) Login: Verb:GET, URL:http://localhost:8000/oauth/token

2) Register: Verb:GET, URL:http://localhost:8000/api/register

3) List: Verb:GET, URL:http://localhost:8000/api/products

4) Create: Verb:POST, URL:http://localhost:8000/api/products

5) Show: Verb:GET, URL:http://localhost:8000/api/products/{id}

6) Update: Verb:PUT, URL:http://localhost:8000/api/products/{id}

7) Delete: Verb:DELETE, URL:http://localhost:8000/api/products/{id}

Now simply you can run above listed url like as bellow screen shot:

Login API:

Register API:

Product List API:

Product Create API:

Product Show API:

Product Update API:

Product Delete API:

I hope it can help you...

Thanks for reading ❤

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Angular 8 Pagination Example and Tutorial

Angular 8 Pagination Example and Tutorial

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

<pre class="ql-syntax" spellcheck="false">ng new angular8-simple-pagination-example </pre>

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 <a href="http://localhost:4200" title="" target="_blank">http://localhost:4200</a> on the browser.

Step 2: install ngx-pagination pagination dependency from terminal

So run the below command over terminal

<pre class="ql-syntax" spellcheck="false">npm install ngx-pagination --save </pre>

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 

<pre class="ql-syntax" spellcheck="false">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); } } } </pre>

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

<pre class="ql-syntax" spellcheck="false">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 { } </pre>

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

<pre class="ql-syntax" spellcheck="false"><ul> <li> Emp Name | Emp code</li> <li *ngFor="let item of collection | paginate:{itemsPerPage: 5, currentPage:p}"> {{item.name}} | {{item.code}}</li>  </ul> <pagination-controls (pageChange)="p=$event"></pagination-controls> </pre>

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 <a href="http://localhost:4200/." target="_blank">http://localhost:4200/.</a> 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 <a href="https://jsonworld.com/demo/server-side-pagination-in-angular-example-and-tutorial" title="" target="_blank">Server Side Pagination in Angular Example and Tutorial</a> . You can also find other demos of<a href="https://jsonworld.com/demo/angular-sample-projects" title="" target="_blank"> Angular Sample Application</a> here to start working on enterprise level application. <a href="https://www.npmjs.com/package/ngx-pagination" title="" target="_blank">Click here</a> to view more about the pagination package over npm.

Originally published by Suraj Roy at jsonworld.com

==========================================

Thanks for reading :heart: If you liked this post, share it with all of your programming buddies! Follow me on <a href="https://www.facebook.com/angular4u" title="" target="_blank">Facebook</a> | <a href="https://twitter.com/codek_tv" title="" target="_blank">Twitter</a>

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☞ <a href="http://learnstartup.net/p/H1jE_tD3l" title="" target="_blank">Angular 8 (formerly Angular 2) - The Complete Guide</a>

☞ <a href="http://learnstartup.net/p/HJigQzgZx" title="" target="_blank">Learn and Understand AngularJS</a>

☞ <a href="http://learnstartup.net/p/ry7Ey9yKW" title="" target="_blank">The Complete Angular Course: Beginner to Advanced</a>

☞ <a href="http://learnstartup.net/p/rkjpGfa5W" title="" target="_blank">Angular Crash Course for Busy Developers</a>

☞ <a href="http://learnstartup.net/p/SkdU19JFZ" title="" target="_blank">Angular Essentials (Angular 2+ with TypeScript)</a>

☞ <a href="http://learnstartup.net/p/B1oHaY8cM" title="" target="_blank">Angular (Full App) with Angular Material, Angularfire & NgRx</a>

☞ <a href="https://l.morioh.com/b0a3f595aa?r=http://learnstartup.net/p/Skf7ILFw3l" title="" target="_blank">Angular & NodeJS - The MEAN Stack Guide</a>

Angular Architecture Patterns and Best Practices (that help to scale)

Angular Architecture Patterns and Best Practices (that help to scale)
<p class="ql-align-center">Originally published by Bartosz Pietrucha at angular-academy.com</p><p> In order to deal with mentioned factors to maintain a high quality of delivery and prevent technical debt, robust and well-grounded architecture is necessary. Angular itself is a quite opinionated framework, forcing developers to do things the proper way, yet there are a lot of places where things can go wrong. In this article, I will present high-level recommendations of well-designed Angular application architecture based on best practices and battle-proven patterns. Our ultimate goal in this article is to learn how to design Angular application in order to maintain sustainable development speed and ease of adding new features in the long run. To achieve these goals, we will apply:</p>
    <li>proper abstractions between application layers,</li><li>unidirectional data flow,</li><li>reactive state management,</li><li>modular design,</li><li>smart and dumb components pattern.</li>
<p></p>

Problems of scalability in front-end

<p>Let's think about problems in terms of scalability we can face in the development of modern front-end applications. Today, front-end applications are not "just displaying" data and accepting user inputs. Single Page Applications (SPAs) are providing users with rich interactions and use backend mostly as a data persistence layer. This means, far more responsibility has been moved to the front-end part of software systems. This leads to a growing complexity of front-end logic, we need to deal with. Not only the number of requirements grows over time, but the amount of data we load into the application is increasing. On top of that, we need to maintain application performance, which can easily be hurt. Finally, our development teams are growing (or at least rotating - people come and go) and it is important for new-comers to get up to speed as fast as possible.</p><p></p><p>One of the solutions to the problems described above is solid system architecture. But, this comes with the cost, the cost of investing in that architecture from day one. It can be very tempting for us developers, to deliver new features very quickly, when the system is still very small. At this stage, everything is easy and understandable, so development goes really fast. But, unless we care about the architecture, after a few developers rotations, tricky features, refactorings, a couple of new modules, the speed of development slows down radically. Below diagram presents how it usually looked like in my development career. This is not any scientifical study, it's just how I see it.</p><p></p>

Software architecture

<p>To discuss architecture best practices and patterns, we need to answer a question, what the software architecture is, in the first place. Martin Fowlerdefines architecture as "highest-level breakdown of a system into its parts". On top of that, I would say that software architecture describes how the software is composed of its parts and what are the rules and constraints of the communication between those parts. Usually, the architectural decisions that we make in our system development, are hard to change as the system grows over time. That's why it is very important to pay attention to those decisions from the very beginning of our project, especially if the software we build is supposed to be running in production for many years. Robert C. Martin once said: the true cost of software is its maintenance. Having well-grounded architecture helps to reduce the costs of the system's maintenance.</p>
Software architecture is the way the software is composed of its parts and the rules and constraints of the communication between those parts

High-level abstraction layers

<p>The first way, we will be decomposing our system, is through the abstraction layers. Below diagram depicts the general concept of this decomposition. The idea is to place the proper responsibility into the proper layer of the system: coreabstraction or presentation layer. We will be looking at each layer independently and analyzing its responsibility. This division of the system also dictates communication rules. For example, the presentation layer can talk to the core layer only through the abstractionlayer. Later, we will learn what are the benefits of this kind of constraint.</p><p></p>

Presentation layer

<p>Let's start analyzing our system break-down from the presentation layer. This is the place where all our Angular components live. The only responsibilities of this layer are to present and to delegate. In other words, it presents the UI and delegates user's actions to the core layer, through the abstraction layer. It knows what to display and what to do, but it does not know how the user's interactions should be handled.</p><p>Below code snippet contains CategoriesComponent using SettingsFacadeinstance from abstraction layer to delegate user's interaction (via addCategory() and updateCategory()) and present some state in its template (via isUpdating$).</p><pre class="ql-syntax" spellcheck="false">@Component({ selector: 'categories', templateUrl: './categories.component.html', styleUrls: ['./categories.component.scss'] }) export class CategoriesComponent implements OnInit {

@Input() cashflowCategories$: CashflowCategory[];
newCategory: CashflowCategory = new CashflowCategory();
isUpdating$: Observable<boolean>;

constructor(private settingsFacade: SettingsFacade) {
this.isUpdating$ = settingsFacade.isUpdating$();
}

ngOnInit() {
this.settingsFacade.loadCashflowCategories();
}

addCategory(category: CashflowCategory) {
this.settingsFacade.addCashflowCategory(category);
}

updateCategory(category: CashflowCategory) {
this.settingsFacade.updateCashflowCategory(category);
}

}
</pre>

Abstraction layer

<p>The abstraction layer decouples the presentation layer from the core layer and also has it's very own defined responsibilities. This layer exposes the streams of state and interface for the components in the presentation layer, playing the role of the facade. This kind of facade sandboxes what components can see and do in the system. We can implement facades by simply using Angular class providers. The classes here may be named with Facade postfix, for example SettingsFacade. Below, you can find an example of such a facade.</p><pre class="ql-syntax" spellcheck="false">@Injectable()
export class SettingsFacade {

constructor(private cashflowCategoryApi: CashflowCategoryApi, private settingsState: SettingsState) { }

isUpdating$(): Observable<boolean> {
return this.settingsState.isUpdating$();
}

getCashflowCategories$(): Observable<CashflowCategory[]> {
// here we just pass the state without any projections
// it may happen that it is necessary to combine two or more streams and expose to the components
return this.settingsState.getCashflowCategories$();
}

loadCashflowCategories() {
return this.cashflowCategoryApi.getCashflowCategories()
.pipe(tap(categories => this.settingsState.setCashflowCategories(categories)));
}

// optimistic update
// 1. update UI state
// 2. call API
addCashflowCategory(category: CashflowCategory) {
this.settingsState.addCashflowCategory(category);
this.cashflowCategoryApi.createCashflowCategory(category)
.subscribe(
(addedCategoryWithId: CashflowCategory) => {
// success callback - we have id generated by the server, let's update the state
this.settingsState.updateCashflowCategoryId(category, addedCategoryWithId)
},
(error: any) => {
// error callback - we need to rollback the state change
this.settingsState.removeCashflowCategory(category);
console.log(error);
}
);
}

// pessimistic update
// 1. call API
// 2. update UI state
updateCashflowCategory(category: CashflowCategory) {
this.settingsState.setUpdating(true);
this.cashflowCategoryApi.updateCashflowCategory(category)
.subscribe(
() => this.settingsState.updateCashflowCategory(category),
(error) => console.log(error),
() => this.settingsState.setUpdating(false)
);
}
}
</pre>

Abstraction interface

<p>We already know the main responsibilities for this layer; to expose streams of state and interface for the components. Let's start with the interface. Public methods loadCashflowCategories()addCashflowCategory() and updateCashflowCategory() abstract away the details of state management and the external API calls from the components. We are not using API providers (like CashflowCategoryApi) in components directly, as they live in the core layer. Also, how the state changes is not a concern of the components. The presentation layer should not care about how things are done and components should just call the methods from the abstraction layer when necessary (delegate). Looking at the public methods in our abstraction layer should give us a quick insight about high-level use casesin this part of the system.</p><p>But we should remember that the abstraction layer is not a place to implement business logic. Here we just want to connect the presentation layer to our business logic, abstracting the way it is connected.</p>

State

<p>When it comes to the state, the abstraction layer makes our components independent of the state management solution. Components are given Observables with data to display on the templates (usually with async pipe) and don't care how and where this data comes from. To manage our state we can pick any state management library that supports RxJS (like NgRx) or simple use BehaviorSubjects to model our state. In the example above we are using state object that internally uses BehaviorSubjects (state object is a part of our core layer). In the case of NgRx, we would dispatch actions for the store.</p><p>Having this kind abstraction gives us a lot of flexibility and allows to change the way we manage state not even touching the presentation layer. It's even possible to seamlessly migrate to a real-time backend like Firebase, making our application real-time. I personally like to start with BehaviorSubjects to manage the state. If later, at some point in the development of the system, there is a need to use something else, with this kind of architecture, it is very easy to refactor.</p>

Synchronization strategy

<p>Now, let's take a closer look at the other important aspect of the abstraction layer. Regardless of the state management solution we choose, we can implement UI updates in either optimistic or pessimistic fashion. Imagine we want to create a new record in the collection of some entities. This collection was fetched from the backend and displayed in the DOM. In a pessimistic approach, we first try to update the state on the backend side (for example with HTTP request) and in case of success we update the state in the frontend application. On the other hand, in an optimistic approach, we do it in a different order. First, we assume that the backend update will succeed and update frontend state immediately. Then we send request to update server state. In case of success, we don't need to do anything, but in case of failure, we need to rollback the change in our frontend application and inform the user about this situation.</p>
Optimistic update changes the UI state first and attempts to update the backend state. This provides a user with a better experience, as he does not see any delays, because of network latency. If backend update fails, then UI change has to be rolled back.
Pessimistic update changes the backend state first and only in case of success updates the UI state. Usually, it is necessary to show some kind of spinner or loading bar during the execution of backend request, because of network latency.

Caching

<p>Sometimes, we may decide that the data we fetch from the backend will not be a part of our application state. This may be useful for read-only data that we don't want to manipulate at all and just pass (via abstraction layer) to the components. In this case, we can apply data caching in our facade. The easiest way to achieve it is to use shareReplay() RxJS operator that will replay the last value in the stream for each new subscriber. Take a look at the code snippet below with RecordsFacade using RecordsApi to fetch, cache and filter the data for the components.</p><pre class="ql-syntax" spellcheck="false">@Injectable()
export class RecordsFacade {

private records$: Observable<Record[]>;

constructor(private recordApi: RecordApi) {
this.records$ = this.recordApi
.getRecords()
.pipe(shareReplay(1)); // cache the data
}

getRecords() {
return this.records$;
}

// project the cached data for the component
getRecordsFromPeriod(period?: Period): Observable<Record[]> {
return this.records$
.pipe(map(records => records.filter(record => record.inPeriod(period))));
}

searchRecords(search: string): Observable<Record[]> {
return this.recordApi.searchRecords(search);
}
}
</pre><p>To sum up, what we can do in the abstraction layer is to:</p>

    <li>expose methods for the components in which we:</li><li class="ql-indent-1">delegate logic execution to the core layer,</li><li class="ql-indent-1">decide about data synchronization strategy (optimistic vs. pessimistic),</li><li>expose streams of state for the components:</li><li class="ql-indent-1">pick one or more streams of UI state (and combine them if necessary),</li><li class="ql-indent-1">cache data from external API.</li>
<p>As we see, the abstraction layer plays an important role in our layered architecture. It has clearly defined responsibilities what helps to better understand and reason about the system. Depending on your particular case, you can create one facade per Angular module or one per each entity. For example, the SettingsModule may have a single SettingsFacade, if it's not too bloated. But sometimes it may be better to create more-granular abstraction facades for each entity individually, like UserFacade for Userentity.</p>

Core layer

<p>The last layer is the core layer. Here is where core application logic is implemented. All data manipulation and outside world communicationhappen here. If for state management, we were using a solution like NgRx, here is a place to put our state definition, actions and reducers. Since in our examples we are modeling state with BehaviorSubjects, we can encapsulate it in a convenient state class. Below, you can find SettingsState example from the core layer.</p><pre class="ql-syntax" spellcheck="false">@Injectable()
export class SettingsState {

private updating$ = new BehaviorSubject<boolean>(false);
private cashflowCategories$ = new BehaviorSubject<CashflowCategory[]>(null);

isUpdating$() {
return this.updating$.asObservable();
}

setUpdating(isUpdating: boolean) {
this.updating$.next(isUpdating);
}

getCashflowCategories$() {
return this.cashflowCategories$.asObservable();
}

setCashflowCategories(categories: CashflowCategory[]) {
this.cashflowCategories$.next(categories);
}

addCashflowCategory(category: CashflowCategory) {
const currentValue = this.cashflowCategories$.getValue();
this.cashflowCategories$.next([...currentValue, category]);
}

updateCashflowCategory(updatedCategory: CashflowCategory) {
const categories = this.cashflowCategories$.getValue();
const indexOfUpdated = categories.findIndex(category => category.id === updatedCategory.id);
categories[indexOfUpdated] = updatedCategory;
this.cashflowCategories$.next([...categories]);
}

updateCashflowCategoryId(categoryToReplace: CashflowCategory, addedCategoryWithId: CashflowCategory) {
const categories = this.cashflowCategories$.getValue();
const updatedCategoryIndex = categories.findIndex(category => category === categoryToReplace);
categories[updatedCategoryIndex] = addedCategoryWithId;
this.cashflowCategories$.next([...categories]);
}

removeCashflowCategory(categoryRemove: CashflowCategory) {
const currentValue = this.cashflowCategories$.getValue();
this.cashflowCategories$.next(currentValue.filter(category => category !== categoryRemove));
}
}
</pre><p>In the core layer, we also implement HTTP queries in the form of class providers. This kind of class could have Api or Service name postfix. API services have only one responsibility - it is just to communicate with API endpoints and nothing else. We should avoid any caching, logic or data manipulation here. A simple example of API service can be found below.</p><pre class="ql-syntax" spellcheck="false">@Injectable()
export class CashflowCategoryApi {

readonly API = '/api/cashflowCategories';

constructor(private http: HttpClient) {}

getCashflowCategories(): Observable<CashflowCategory[]> {
return this.http.get<CashflowCategory[]>(this.API);
}

createCashflowCategory(category: CashflowCategory): Observable<any> {
return this.http.post(this.API, category);
}

updateCashflowCategory(category: CashflowCategory): Observable<any> {
return this.http.put(${this.API}/${category.id}, category);
}

}
</pre><p>In this layer, we could also place any validators, mappers or more advanced use-cases that require manipulating many slices of our UI state.</p><p>We have covered the topic of the abstraction layers in our frontend application. Every layer has it's well-defined boundaries and responsibilities. We also defined the strict rules of communication between layers. This all helps to better understand and reason about the system over time as it becomes more and more complex.</p><p></p><p>If you need help with your project, check out Angualar Academy Workshops or write an email to [email protected].</p>

Unidirectional data flow and reactive state management

<p>The next principle we want to introduce in our system is about the data flow and propagation of change. Angular itself uses unidirectional data flow on presentation level (via input bindings), but we will impose a similar restriction on the application level. Together with reactive state management (based on streams), it will give us the very important property of the system - data consistency. Below diagram presents the general idea of unidirectional data flow.</p><p></p><p>Whenever any model value change in our application, Angular change detection system takes care of the propagation of that change. It does it via input property bindings from the top to bottom of the whole component tree. It means that a child component can only depend on its parent and never vice versa. This is why we call it unidirectional data flow. This allows Angular to traverse the components tree only once (as there are no cycles in the tree structure) to achieve a stable state, which means that every value in the bindings is propagated.</p><p>As we know from previous chapters, there is the core layer above the presentation layer, where our application logic is implemented. There are the services and providers that operate on our data. What if we apply the same principle of data manipulation on that level? We can place the application data (the state) in one place "above" the components and propagate the values down to the components via Observable streams (Redux and NgRx call this place a store). The state can be propagated to multiple components and displayed in multiple places, but never modified locally. The change may come only "from above" and the components below only "reflect" the current state of the system. This gives us the important system's property mentioned before - data consistency - and the state object becomes the single source of truth. Practically speaking, we can display the same data in multiple places and not be afraid that the values would differ.</p><p>Our state object exposes the methods for the services in our core layer to manipulate the state. Whenever there is a need to change the state, it can happen only by calling a method on the state object (or dispatching an action in case of using NgRx). Then, the change is propagated "down", via streams, the to presentation layer (or any other service). This way, our state management is reactive. Moreover, with this approach, we also increase the level of predictability in our system, because of strict rules of manipulating and sharing the application state. Below you can find a code snippet modeling the state with BehaviorSubjects.</p><pre class="ql-syntax" spellcheck="false">@Injectable()
export class SettingsState {

private updating$ = new BehaviorSubject<boolean>(false);
private cashflowCategories$ = new BehaviorSubject<CashflowCategory[]>(null);

isUpdating$() {
return this.updating$.asObservable();
}

setUpdating(isUpdating: boolean) {
this.updating$.next(isUpdating);
}

getCashflowCategories$() {
return this.cashflowCategories$.asObservable();
}

setCashflowCategories(categories: CashflowCategory[]) {
this.cashflowCategories$.next(categories);
}

addCashflowCategory(category: CashflowCategory) {
const currentValue = this.cashflowCategories$.getValue();
this.cashflowCategories$.next([...currentValue, category]);
}

updateCashflowCategory(updatedCategory: CashflowCategory) {
const categories = this.cashflowCategories$.getValue();
const indexOfUpdated = categories.findIndex(category => category.id === updatedCategory.id);
categories[indexOfUpdated] = updatedCategory;
this.cashflowCategories$.next([...categories]);
}

updateCashflowCategoryId(categoryToReplace: CashflowCategory, addedCategoryWithId: CashflowCategory) {
const categories = this.cashflowCategories$.getValue();
const updatedCategoryIndex = categories.findIndex(category => category === categoryToReplace);
categories[updatedCategoryIndex] = addedCategoryWithId;
this.cashflowCategories$.next([...categories]);
}

removeCashflowCategory(categoryRemove: CashflowCategory) {
const currentValue = this.cashflowCategories$.getValue();
this.cashflowCategories$.next(currentValue.filter(category => category !== categoryRemove));
}
}

</pre><p>Let's recap the steps of handling the user interaction, having in mind all the principles we have already introduced. First, let's imagine that there is some event in the presentation layer (for example button click). The component delegates the execution to the abstraction layer, calling the method on the facade settingsFacade.addCategory(). Then, the facade calls the methods on the services in the core layer - categoryApi.create() and settingsState.addCategory(). The order of invocation of those two methods depends on synchronization strategy we choose (pessimistic or optimistic). Finally, the application state is propagated down to the presentation layer via the observable streams. This process is well-defined.</p><p></p>

Modular design

<p>We have covered the horizontal division in our system and the communication patterns across it. Now we are going to introduce a vertical separation into feature modules. The idea is to slice the application into feature modules representing different business functionalities. This is yet another step to deconstruct the system into smaller pieces for better maintainability. Each of the features modules share the same horizontal separation of the core, abstraction, and presentation layer. It is important to note, that these modules could be lazily loaded (and preloaded) into the browser increasing the initial load time of the application. Below you can find a diagram illustrating features modules separation.</p><p></p><p>Our application has also two additional modules for more technical reasons. We have a CoreModule that defines our singleton services, single-instance components, configuration, and export any third-party modules needed in AppModule. This module is imported only once in AppModule. The second module is SharedModule that contains common components/pipes/directives and also export commonly used Angular modules (like CommonModule). SharedModule can be imported by any feature module. The diagram below presents the imports structure.</p><p></p>

Module directory structure

<p>Below diagram presents how we can place all the pieces of our SettingsModule inside the directories. We can put the files inside of the folders with a name representing their function.</p><p></p>

Smart and dumb components

<p>The final architectural pattern we introduce in this article is about components themselves. We want to divide components into two categories, depending on their responsibilities. First, are the smart components (aka containers). These components usually:</p>
    <li>have facade/s and other services injected,</li><li>communicate with the core layer,</li><li>pass data to the dumb components,</li><li>react to the events from dumb components,</li><li>are top-level routable components (but not always!).</li>
<p>Previously presented CategoriesComponent is smart. It has SettingsFacadeinjected and uses it to communicate with the core layer of our application.</p><p>In the second category, there are dumb components (aka presentational). Their only responsibilities are to present UI element and to delegate user interaction "up" to the smart components via events. Think of a native HTML element like <button>Click me</button>. That element does not have any particular logic implemented. We can think of the text 'Click me' as an input for this component. It also has some events that can be subscribed to, like click event. Below you can find a code snippet of a simple presentational component with one input and no output events.</p><pre class="ql-syntax" spellcheck="false">@Component({
selector: 'budget-progress',
templateUrl: './budget-progress.component.html',
styleUrls: ['./budget-progress.component.scss'],
changeDetection: ChangeDetectionStrategy.OnPush
})
export class BudgetProgressComponent {

@Input()
budget: Budget;
today: string;

}
</pre>

Summary

<p>We have covered a couple of ideas on how to design the architecture of an Angular application. These principles, if applied wisely, can help to maintain sustainable development speed over time, and allow new features to be delivered easily. Please don't treat them as some strict rules, but rather recommendations that could be employed when they make sense.</p><p>We have taken a close look at the abstractions layers, unidirectional data flow, and reactive state management, modular design, and smart/dumb components pattern. I hope that these concepts will be helpful in your projects and, as always, if you have any questions, I am more than happy to chat with you.</p><p class="ql-align-center">Originally published by Bartosz Pietrucha at angular-academy.com</p><p>==========================================</p><p>Thanks for reading :heart: If you liked this post, share it with all of your programming buddies! Follow me on Facebook | Twitter</p>

Learn More

<p>☞ Angular 8 (formerly Angular 2) - The Complete Guide</p><p>☞ Complete Angular 8 from Zero to Hero | Get Hired</p><p>☞ Learn and Understand AngularJS</p><p>☞ The Complete Angular Course: Beginner to Advanced</p><p>☞ Angular Crash Course for Busy Developers</p><p>☞ Angular Essentials (Angular 2+ with TypeScript)</p><p>☞ Angular (Full App) with Angular Material, Angularfire & NgRx</p><p>☞ Angular & NodeJS - The MEAN Stack Guide</p>