Edward Jackson

Edward Jackson

1558706188

A Beginner’s Guide to GraphQL

One of the most commonly discussed terms today is the API. A lot of people don’t know exactly what an API is. Basically, API stands for Application Programming Interface. It is, as the name says, an interface with which people — developers, users, consumers — can interact with data.

You can think of an API as a bartender. You ask the bartender for a drink, and they give you what you wanted. Simple. So why is that a problem?

Since the start of the modern web, building APIs has not been as hard as it sounds. But learning and understanding APIs was. Developers form the majority of the people that will use your API to build something or just consume data. So your API should be as clean and as intuitive as possible. A well-designed API is very easy to use and learn. It’s also intuitive, a good point to keep in mind when you’re starting to design your API.

We’ve been using REST to build APIs for a long time. Along with that comes some problems. When building an API using REST design, you’ll face some problems like:

  1. you’ll have a lot of endpoints

  2. it’ll be much harder for developers to learn and understand your API

  3. there is over- and under-fetching of information

To solve these problems, Facebook created GraphQL. Today, I think GraphQL is the best way to build APIs. This article will tell you why you should start to learn it today.

In this article, you’re going to l_earn how GraphQL work_s. I’m going to show you how to create a very well-designed, efficient, powerful API using GraphQL.

You’ve probably already heard about GraphQL, as a lot of people and companies are using it. Since GraphQL is open-source, its community has grown huge.

Now, it’s time for you start to learn in practice how GraphQL works and all about its magic.

What is GraphQL?

GraphQL is an open-source query language developed by Facebook. It provides us with a more efficient way design, create, and consume our APIs. Basically, it’s the replacement for REST.

GraphQL has a lot of features, like:

  1. You write the data that you want, and you get exactly the data that you want. No more over-fetching of information as we are used to with REST.
  2. It gives us a single endpoint, no more version 2 or version 3 for the same API.
  3. GraphQL is strongly-typed, and with that you can validate a query within the GraphQL type system before execution. It helps us build more powerful APIs.

This is a basic introduction to GraphQL — why it’s so powerful and why it’s gaining a lot of popularity these days. If you want to learn more about it, I recommend you to go the GraphQL website and check it out.

Getting started

The main objective in this article is not to learn how to set up a GraphQL server, so we’re not getting deep into that for now. The objective is to learn how GraphQL works in practice, so we’re gonna use a zero-configuration GraphQL server called ☄️ Graphpack.

To start our project, we’re going to create a new folder and you can name it whatever you want. I’m going to name it graphql-server:

Open your terminal and type:

mkdir graphql-server

Now, you should have npm or yarn installed in your machine. If you don’t know what these are, npm and yarn are package managers for the JavaScript programming language. For Node.js, the default package manager is npm.

Inside your created folder type the following command:

npm init -y 

Or if you use yarn:

yarn init 

npm will create a package.json file for you, and all the dependencies that you installed and your commands will be there.

So now, we’re going to install the only dependency that we’re going to use.

☄️Graphpack lets you create a GraphQL server with zero configuration. Since we’re just starting with GraphQL, this will help us a lot to go on and learn more without getting worried about a server configuration.

In your terminal, inside your root folder, install it like this:

npm install --save-dev graphpack 

Or, if you use yarn, you should go like this:

yarn add --dev graphpack 

After Graphpack is installed, go to our scripts in package.json file, and put the following code there:

"scripts": {
    "dev": "graphpack",
    "build": "graphpack build"
 }

We’re going to create a folder called src, and it’s going to be the only folder in our entire server.

Create a folder called src, after that, inside our folder, we’re going to create three files only.

Inside our src folder create a file called schema.graphql. Inside this first file, put the following code:

type Query {    
    hello: String    
}

In this schema.graphql file is going to be our entire GraphQL schema. If you don’t know what it is, I’ll explain later — don’t worry.

Now, inside our src folder, create a second file. Call it resolvers.js and, inside this second file, put the following code:

import { users } from "./db";

const resolvers = {    
    Query: {    
        hello: () => "Hello World!"    
    }    
};

export default resolvers;

This resolvers.js file is going to be the way we provide the instructions for turning a GraphQL operation into data.

And finally, inside your src folder, create a third file. Call this db.js and, inside this third file, put the following code:

export let users = [    
    { id: 1, name: "John Doe", email: "john@gmail.com", age: 22 },    
    { id: 2, name: "Jane Doe", email: "jane@gmail.com", age: 23 }    
];

In this tutorial we’re not using a real-world database. So this db.js file is going to simulate a database, just for learning purposes.

Now our src folder should look like this:

src
  |--db.js
  |--resolvers.js
  |--schema.graphql

Now, if you run the command npm run dev or, if you’re using yarn, yarn dev, you should see this output in your terminal:

A Beginner’s Guide to GraphQL

You can now go to localhost:4000. This means that we’re ready to go and start writing our first queries, mutations, and subscriptions in GraphQL.

You see the GraphQL Playground, a powerful GraphQL IDE for better development workflows. If you want to learn more about GraphQL Playground, click here.

Schema

GraphQL has its own type of language that’s used to write schemas. This is a human-readable schema syntax called Schema Definition Language (SDL). The SDL will be the same, no matter what technology you’re using — you can use this with any language or framework that you want.

This schema language its very helpful because it’s simple to understand what types your API is going to have. You can understand it just by looking right it.

Types

Types are one of the most important features of GraphQL. Types are custom objects that represent how your API is going to look. For example, if you’re building a social media application, your API should have types such as Posts, Users, Likes, Groups.

Types have fields, and these fields return a specific type of data. For example, we’re going to create a User type, we should have some name, email, and age fields. Type fields can be anything, and always return a type of data as Int, Float, String, Boolean, ID, a List of Object Types, or Custom Objects Types.

So now to write our first Type, go to your schema.graphql file and replace the type Query that is already there with the following:

type User {    
    id: ID!    
    name: String!    
    email: String!    
    age: Int    
}

Each User is going to have an ID, so we gave it an ID type. User is also going to have a name and email, so we gave it a String type, and an age, which we gave an Int type. Pretty simple, right?

But, what about those ! at the end of every line? The exclamation point means that the fields are non-nullable, which means that every field must return some data in each query. The only nullable field that we’re going to have in our User type will be age.

In GraphQL, you will deal with three main concepts:

  1. queries — the way you’re going to get data from the server.
  2. mutations — the way you’re going to modify data on the server and get updated data back (create, update, delete).
  3. subscriptions — the way you’re going to maintain a real-time connection with the server.

I’m going to explain all of them to you. Let’s start with Queries.

Queries

To explain this in a simple way, queries in GraphQL are how you’re going to get data. One of the most beautiful things about queries in GraphQL is that you are just going to get the exact data that you want. No more, no less. This has a huge positive impact in our API — no more over-fetching or under-fetching information as we had with REST APIs.

We’re going to create our first type Query in GraphQL. All our queries will end up inside this type. So to start, we’ll go to our schema.graphql and write a new type called Query:

type Query {    
    users: [User!]!    
}

It’s very simple: the users query will return to us an array of one or more Users. It will not return null, because we put in the !, which means it’s a non-nullable query. It should always return something.

But we could also return a specific user. For that we’re going to create a new query called user. Inside our Query type, put the following code:

user(id: ID!): User! 

Now our Query type should look like this:

type Query {    
    users: [User!]!    
    user(id: ID!): User!    
}

As you see, with queries in GraphQL we can also pass arguments. In this case, to query for a specific user, we’re going to pass its ID.

But, you may be wondering: how does GraphQL know where get the data? That’s why we should have a resolvers.js file. That file tells GraphQL how and where it’s going to fetch the data.

First, go to our resolvers.js file and import the db.js that we just created a few moments ago. Your resolvers.js file should look like this:

import { users } from "./db";

const resolvers = {    
    Query: {    
        hello: () => "Hello World!"    
    }    
};

export default resolvers;

Now, we’re going to create our first Query. Go to your resolvers.js file and replace the hello function. Now your Query type should look like this:

import { users } from "./db";

const resolvers = {    
    Query: {    
        user: (parent, { id }, context, info) => {    
        return users.find(user => user.id === id);    
        },    
        users: (parent, args, context, info) => {    
            return users;    
        }    
    }    
};

export default resolvers;

Now, to explain how is it going to work:

Each query resolver has four arguments. In the user function, we’re going to pass id as an argument, and then return the specific user that matches the passed id. Pretty simple.

In the users function, we’re just going to return the users array that already exists. It’ll always return to us all of our users.

Now, we’re going to test if our queries are working fine. Go to localhost:4000 and put in the following code:

query {    
    users {    
        id    
        name    
        email    
        age    
    }    
}

It should return to you all of our users.

Or, if you want to return a specific user:

query {    
    user(id: 1) {    
        id    
        name    
        email    
        age    
    }    
}

Now, we’re going to start learning about mutations, one of the most important features in GraphQL.

Mutations

In GraphQL, mutations are the way you’re going to modify data on the server and get updated data back. You can think like the CUD (Create, Update, Delete) of REST .

We’re going to create our first type mutation in GraphQL, and all our mutations will end up inside this type. So, to start, go to our schema.graphql and write a new type called mutation:

type Mutation {    
    createUser(id: ID!, name: String!, email: String!, age: Int): User!    
    updateUser(id: ID!, name: String, email: String, age: Int): User!    
    deleteUser(id: ID!): User!    
}

As you can see, we’re going to have three mutations:

createUser: we should pass an ID, name, email, and age. It should return a new user to us.

updateUser: we should pass an ID, and a new name, email, or age. It should return a new user to us.

deleteUser: we should pass an ID. It should return the deleted user to us.

Now, go to our resolvers.js file and below the Query object, create a new mutation object like this:

Mutation: {    
    createUser: (parent, { id, name, email, age }, context, info) => {    
        const newUser = { id, name, email, age };    
        users.push(newUser);    
        return newUser;    
},   
    updateUser: (parent, { id, name, email, age }, context, info) => {    
        let newUser = users.find(user => user.id === id);    
        newUser.name = name;    
        newUser.email = email;    
        newUser.age = age;

        return newUser;
    },    
    deleteUser: (parent, { id }, context, info) => {    
        const userIndex = users.findIndex(user => user.id === id);

        if (userIndex === -1) throw new Error("User not found.");

        const deletedUsers = users.splice(userIndex, 1);

        return deletedUsers[0];     
    }    
}

Now, our resolvers.js file should look like this:

import { users } from "./db";

const resolvers = {    
    Query: {        
        user: (parent, { id }, context, info) => {      
            return users.find(user => user.id === id);      
        },      
        users: (parent, args, context, info) => {       
            return users;       
        }       
    },    
    Mutation: {    
        createUser: (parent, { id, name, email, age }, context, info) => {    
            const newUser = { id, name, email, age };    
            users.push(newUser);    
            return newUser;    
    },   
        updateUser: (parent, { id, name, email, age }, context, info) => {    
            let newUser = users.find(user => user.id === id);    
            newUser.name = name;    
            newUser.email = email;    
            newUser.age = age;

            return newUser;
        },    
        deleteUser: (parent, { id }, context, info) => {    
            const userIndex = users.findIndex(user => user.id === id);

            if (userIndex === -1) throw new Error("User not found.");

            const deletedUsers = users.splice(userIndex, 1);

            return deletedUsers[0];         
        }    
    }    
};

export default resolvers;

Now, we’re going to test if our mutations are working fine. Go to localhost:4000 and put in the following code:

mutation {    
    createUser(id: 3, name: "Robert", email: "robert@gmail.com", age: 21) {    
        id    
        name    
        email    
        age    
    }    
}

It should return a new user to you. If you want to try making new mutations, I recommend you to try for yourself! Try to delete this same user that you created to see if it’s working fine.

Finally, we’re going to start learning about subscriptions, and why they are so powerful.

Subscriptions

As I said before, subscriptions are the way you’re going to maintain a real-time connection with a server. That means that whenever an event occurs in the server and whenever that event is called, the server will send the corresponding data to the client.

By working with subscriptions, you can keep your app updated to the latest changes between different users.

A Beginner’s Guide to GraphQL

A basic subscription is like this:

subscription {    
    users {    
        id    
        name    
        email    
        age    
    }    
}

You will say it’s very similar to a query, and yes it is. But it works differently.

When something is updated in the server, the server will run the GraphQL query specified in the subscription, and send a newly updated result to the client.

We’re not going to work with subscriptions in this specific article, but if you want to read more about them click here.

Conclusion

As you have seen, GraphQL is a new technology that is really powerful. It gives us real power to build better and well-designed APIs. That’s why I recommend you start to learn it now. For me, it will eventually replace REST.

#graphql #rest #api

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Buddha Community

A Beginner’s Guide to GraphQL
Mike  Kozey

Mike Kozey

1656151740

Test_cov_console: Flutter Console Coverage Test

Flutter Console Coverage Test

This small dart tools is used to generate Flutter Coverage Test report to console

How to install

Add a line like this to your package's pubspec.yaml (and run an implicit flutter pub get):

dev_dependencies:
  test_cov_console: ^0.2.2

How to run

run the following command to make sure all flutter library is up-to-date

flutter pub get
Running "flutter pub get" in coverage...                            0.5s

run the following command to generate lcov.info on coverage directory

flutter test --coverage
00:02 +1: All tests passed!

run the tool to generate report from lcov.info

flutter pub run test_cov_console
---------------------------------------------|---------|---------|---------|-------------------|
File                                         |% Branch | % Funcs | % Lines | Uncovered Line #s |
---------------------------------------------|---------|---------|---------|-------------------|
lib/src/                                     |         |         |         |                   |
 print_cov.dart                              |  100.00 |  100.00 |   88.37 |...,149,205,206,207|
 print_cov_constants.dart                    |    0.00 |    0.00 |    0.00 |    no unit testing|
lib/                                         |         |         |         |                   |
 test_cov_console.dart                       |    0.00 |    0.00 |    0.00 |    no unit testing|
---------------------------------------------|---------|---------|---------|-------------------|
 All files with unit testing                 |  100.00 |  100.00 |   88.37 |                   |
---------------------------------------------|---------|---------|---------|-------------------|

Optional parameter

If not given a FILE, "coverage/lcov.info" will be used.
-f, --file=<FILE>                      The target lcov.info file to be reported
-e, --exclude=<STRING1,STRING2,...>    A list of contains string for files without unit testing
                                       to be excluded from report
-l, --line                             It will print Lines & Uncovered Lines only
                                       Branch & Functions coverage percentage will not be printed
-i, --ignore                           It will not print any file without unit testing
-m, --multi                            Report from multiple lcov.info files
-c, --csv                              Output to CSV file
-o, --output=<CSV-FILE>                Full path of output CSV file
                                       If not given, "coverage/test_cov_console.csv" will be used
-t, --total                            Print only the total coverage
                                       Note: it will ignore all other option (if any), except -m
-p, --pass=<MINIMUM>                   Print only the whether total coverage is passed MINIMUM value or not
                                       If the value >= MINIMUM, it will print PASSED, otherwise FAILED
                                       Note: it will ignore all other option (if any), except -m
-h, --help                             Show this help

example run the tool with parameters

flutter pub run test_cov_console --file=coverage/lcov.info --exclude=_constants,_mock
---------------------------------------------|---------|---------|---------|-------------------|
File                                         |% Branch | % Funcs | % Lines | Uncovered Line #s |
---------------------------------------------|---------|---------|---------|-------------------|
lib/src/                                     |         |         |         |                   |
 print_cov.dart                              |  100.00 |  100.00 |   88.37 |...,149,205,206,207|
lib/                                         |         |         |         |                   |
 test_cov_console.dart                       |    0.00 |    0.00 |    0.00 |    no unit testing|
---------------------------------------------|---------|---------|---------|-------------------|
 All files with unit testing                 |  100.00 |  100.00 |   88.37 |                   |
---------------------------------------------|---------|---------|---------|-------------------|

report for multiple lcov.info files (-m, --multi)

It support to run for multiple lcov.info files with the followings directory structures:
1. No root module
<root>/<module_a>
<root>/<module_a>/coverage/lcov.info
<root>/<module_a>/lib/src
<root>/<module_b>
<root>/<module_b>/coverage/lcov.info
<root>/<module_b>/lib/src
...
2. With root module
<root>/coverage/lcov.info
<root>/lib/src
<root>/<module_a>
<root>/<module_a>/coverage/lcov.info
<root>/<module_a>/lib/src
<root>/<module_b>
<root>/<module_b>/coverage/lcov.info
<root>/<module_b>/lib/src
...
You must run test_cov_console on <root> dir, and the report would be grouped by module, here is
the sample output for directory structure 'with root module':
flutter pub run test_cov_console --file=coverage/lcov.info --exclude=_constants,_mock --multi
---------------------------------------------|---------|---------|---------|-------------------|
File                                         |% Branch | % Funcs | % Lines | Uncovered Line #s |
---------------------------------------------|---------|---------|---------|-------------------|
lib/src/                                     |         |         |         |                   |
 print_cov.dart                              |  100.00 |  100.00 |   88.37 |...,149,205,206,207|
lib/                                         |         |         |         |                   |
 test_cov_console.dart                       |    0.00 |    0.00 |    0.00 |    no unit testing|
---------------------------------------------|---------|---------|---------|-------------------|
 All files with unit testing                 |  100.00 |  100.00 |   88.37 |                   |
---------------------------------------------|---------|---------|---------|-------------------|
---------------------------------------------|---------|---------|---------|-------------------|
File - module_a -                            |% Branch | % Funcs | % Lines | Uncovered Line #s |
---------------------------------------------|---------|---------|---------|-------------------|
lib/src/                                     |         |         |         |                   |
 print_cov.dart                              |  100.00 |  100.00 |   88.37 |...,149,205,206,207|
lib/                                         |         |         |         |                   |
 test_cov_console.dart                       |    0.00 |    0.00 |    0.00 |    no unit testing|
---------------------------------------------|---------|---------|---------|-------------------|
 All files with unit testing                 |  100.00 |  100.00 |   88.37 |                   |
---------------------------------------------|---------|---------|---------|-------------------|
---------------------------------------------|---------|---------|---------|-------------------|
File - module_b -                            |% Branch | % Funcs | % Lines | Uncovered Line #s |
---------------------------------------------|---------|---------|---------|-------------------|
lib/src/                                     |         |         |         |                   |
 print_cov.dart                              |  100.00 |  100.00 |   88.37 |...,149,205,206,207|
lib/                                         |         |         |         |                   |
 test_cov_console.dart                       |    0.00 |    0.00 |    0.00 |    no unit testing|
---------------------------------------------|---------|---------|---------|-------------------|
 All files with unit testing                 |  100.00 |  100.00 |   88.37 |                   |
---------------------------------------------|---------|---------|---------|-------------------|

Output to CSV file (-c, --csv, -o, --output)

flutter pub run test_cov_console -c --output=coverage/test_coverage.csv

#### sample CSV output file:
File,% Branch,% Funcs,% Lines,Uncovered Line #s
lib/,,,,
test_cov_console.dart,0.00,0.00,0.00,no unit testing
lib/src/,,,,
parser.dart,100.00,100.00,97.22,"97"
parser_constants.dart,100.00,100.00,100.00,""
print_cov.dart,100.00,100.00,82.91,"29,49,51,52,171,174,177,180,183,184,185,186,187,188,279,324,325,387,388,389,390,391,392,393,394,395,398"
print_cov_constants.dart,0.00,0.00,0.00,no unit testing
All files with unit testing,100.00,100.00,86.07,""

Installing

Use this package as an executable

Install it

You can install the package from the command line:

dart pub global activate test_cov_console

Use it

The package has the following executables:

$ test_cov_console

Use this package as a library

Depend on it

Run this command:

With Dart:

 $ dart pub add test_cov_console

With Flutter:

 $ flutter pub add test_cov_console

This will add a line like this to your package's pubspec.yaml (and run an implicit dart pub get):

dependencies:
  test_cov_console: ^0.2.2

Alternatively, your editor might support dart pub get or flutter pub get. Check the docs for your editor to learn more.

Import it

Now in your Dart code, you can use:

import 'package:test_cov_console/test_cov_console.dart';

example/lib/main.dart

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
        // This makes the visual density adapt to the platform that you run
        // the app on. For desktop platforms, the controls will be smaller and
        // closer together (more dense) than on mobile platforms.
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key? key, required this.title}) : super(key: key);

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      // This call to setState tells the Flutter framework that something has
      // changed in this State, which causes it to rerun the build method below
      // so that the display can reflect the updated values. If we changed
      // _counter without calling setState(), then the build method would not be
      // called again, and so nothing would appear to happen.
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Column(
          // Column is also a layout widget. It takes a list of children and
          // arranges them vertically. By default, it sizes itself to fit its
          // children horizontally, and tries to be as tall as its parent.
          //
          // Invoke "debug painting" (press "p" in the console, choose the
          // "Toggle Debug Paint" action from the Flutter Inspector in Android
          // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
          // to see the wireframe for each widget.
          //
          // Column has various properties to control how it sizes itself and
          // how it positions its children. Here we use mainAxisAlignment to
          // center the children vertically; the main axis here is the vertical
          // axis because Columns are vertical (the cross axis would be
          // horizontal).
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

Author: DigitalKatalis
Source Code: https://github.com/DigitalKatalis/test_cov_console 
License: BSD-3-Clause license

#flutter #dart #test 

Abigail betty

Abigail betty

1624226400

What is Bitcoin Cash? - A Beginner’s Guide

Bitcoin Cash was created as a result of a hard fork in the Bitcoin network. The Bitcoin Cash network supports a larger block size than Bitcoin (currently 32mb as opposed to Bitcoin’s 1mb).

Later on, Bitcoin Cash forked into Bitcoin SV due to differences in how to carry on its developments.

That’s Bitcoin Cash in a nutshell. If you want a more detailed review watch the complete video. Here’s what I’ll cover:

0:50 - Bitcoin forks
2:06 - Bitcoin’s block size debate
3:35 - Big blocks camp
4:26 - Small blocks camp
5:16 - Small blocks vs. big blocks arguments
7:05 - How decisions are made in the Bitcoin network
10:14 - Block size debate resolution
11:06 - Bitcoin cash intro
11:28 - BTC vs. BCH
12:13 - Bitcoin Cash (ABC) vs. Bitcoin SV
13:09 - Conclusion
📺 The video in this post was made by 99Bitcoins
The origin of the article: https://www.youtube.com/watch?v=ONhbb4YVRLM
🔺 DISCLAIMER: The article is for information sharing. The content of this video is solely the opinions of the speaker who is not a licensed financial advisor or registered investment advisor. Not investment advice or legal advice.
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#bitcoin #blockchain #bitcoin cash #what is bitcoin cash? - a beginner’s guide #what is bitcoin cash #a beginner’s guide

Elm Graphql: Autogenerate Type-safe GraphQL Queries in Elm

dillonkearns/elm-graphql  

Why use this package over the other available Elm GraphQL packages? This is the only one that generates type-safe code for your entire schema. Check out this blog post, Type-Safe & Composable GraphQL in Elm, to learn more about the motivation for this library. (It's also the only type-safe library with Elm 0.18 or 0.19 support, see this discourse thread).

I built this package because I wanted to have something that:

  1. Gives you type-safe GraphQL queries (if it compiles, it's valid according to the schema),
  2. Creates decoders for you in a seamless and failsafe way, and
  3. Eliminates GraphQL features in favor of Elm language constructs where possible for a simpler UX (for example, GraphQL variables & fragments should just be Elm functions, constants, lets).

See an example in action on Ellie. See more end-to-end example code in the examples/ folder.

Overview

dillonkearns/elm-graphql is an Elm package and accompanying command-line code generator that creates type-safe Elm code for your GraphQL endpoint. You don't write any decoders for your API with dillonkearns/elm-graphql, instead you simply select which fields you would like, similar to a standard GraphQL query but in Elm. For example, this GraphQL query

query {
  human(id: "1001") {
    name
    homePlanet
  }
}

would look like this in dillonkearns/elm-graphql (the code in this example that is prefixed with StarWars is auto-generated)

import Graphql.Operation exposing (RootQuery)
import Graphql.SelectionSet as SelectionSet exposing (SelectionSet)
import StarWars.Object
import StarWars.Object.Human as Human
import StarWars.Query as Query
import StarWars.Scalar exposing (Id(..))


query : SelectionSet (Maybe HumanData) RootQuery
query =
    Query.human { id = Id "1001" } humanSelection


type alias HumanData =
    { name : String
    , homePlanet : Maybe String
    }


humanSelection : SelectionSet HumanData StarWars.Object.Human
humanSelection =
    SelectionSet.map2 HumanData
        Human.name
        Human.homePlanet

GraphQL and Elm are a perfect match because GraphQL is used to enforce the types that your API takes as inputs and outputs, much like Elm's type system does within Elm. elm-graphql simply bridges this gap by making your Elm code aware of your GraphQL server's schema. If you are new to GraphQL, graphql.org/learn/ is an excellent way to learn the basics.

After following the installation instructions to install the @dillonkearns/elm-graphql NPM package and the proper Elm packages (see the Setup section for details). Once you've installed everything, running the elm-graphql code generation tool is as simple as this:

npx elm-graphql https://elm-graphql.herokuapp.com --base StarWars --output examples/src

If headers are required, such as a Bearer Token, the --header flag can be supplied.

npx elm-graphql https://elm-graphql.herokuapp.com --base StarWars --output examples/src --header 'headerKey: header value'

Learning Resources

There is a thorough tutorial in the SelectionSet docs. SelectionSets are the core concept in this library, so I recommend reading through the whole page (it's not very long!).

The examples/ folder is another great place to start.

If you want to learn more GraphQL basics, this is a great tutorial, and a short read: graphql.org/learn/

My Elm Conf 2018 talk goes into the philosophy behind dillonkearns/elm-graphql

Types Without Borders Elm Conf Talk

(Skip to 13:06 to go straight to the dillonkearns/elm-graphql demo).

If you're wondering why code is generated a certain way, you're likely to find an answer in the Frequently Asked Questions (FAQ).

There's a very helpful group of people in the #graphql channel in the Elm Slack. Don't hesitate to ask any questions about getting started, best practices, or just general GraphQL in there!

Setup

dillonkearns/elm-graphql generates Elm code that allows you to build up type-safe GraphQL requests. Here are the steps to setup dillonkearns/elm-graphql.

Add the dillonkearns/elm-graphql elm package as a dependency in your elm.json. You will also need to make sure that elm/json is a dependency of your project since the generated code has lots of JSON decoders in it.

elm install dillonkearns/elm-graphql
elm install elm/json

Install the @dillonkearns/elm-graphql command line tool through npm. This is what you will use to generate Elm code for your API. It is recommended that you save the @dillonkearns/elm-graphql command line tool as a dev dependency so that everyone on your project is using the same version.

npm install --save-dev @dillonkearns/elm-graphql
# you can now run it locally using `npx elm-graphql`,
# or by calling it through an npm script as in this project's package.json

Run the @dillonkearns/elm-graphql command line tool installed above to generate your code. If you used the --save-dev method above, you can simply create a script in your package.json like the following:

{
  "name": "star-wars-elm-graphql-project",
  "version": "1.0.0",
  "scripts": {
    "api": "elm-graphql https://elm-graphql.herokuapp.com/api --base StarWars"
  }

With the above in your package.json, running npm run api will generate dillonkearns/elm-graphql code for you to call in ./src/StarWars/. You can now use the generated code as in this Ellie example or in the examples folder.

Subscriptions Support

You can do real-time APIs using GraphQL Subscriptions and dillonkearns/elm-graphql. Just wire in the framework-specific JavaScript code for opening the WebSocket connection through a port. Here's a live demo and its source code. The demo server is running Elixir/Absinthe.

Contributors

Thank you Mario Martinez (martimatix) for all your feedback, the elm-format PR, and for the incredible logo design!

Thank you Mike Stock (mikeastock) for setting up Travis CI!

Thanks for the reserved words pull request @madsflensted!

A huge thanks to @xtian for doing the vast majority of the 0.19 upgrade work! :tada:

Thank you Josh Adams (@knewter) for the code example for Subscriptions with Elixir/Absinthe wired up through Elm ports!

Thank you Romario for adding OptionalArgument.map!

Thank you Aaron White for your pull request to improve the performance and stability of the elm-format step! 🎉

Roadmap

All core features are supported. That is, you can build any query or mutation with your dillonkearns/elm-graphql-generated code, and it is guaranteed to be valid according to your server's schema.

dillonkearns/elm-graphql will generate code for you to generate subscriptions and decode the responses, but it doesn't deal with the low-level details for how to send them over web sockets. To do that, you will need to use custom code or a package that knows how to communicate over websockets (or whichever protocol) to setup a subscription with your particular framework. See this discussion for why those details are not handled by this library directly.

I would love to hear feedback if you are using GraphQL Subscriptions. In particular, I'd love to see live code examples to drive any improvements to the Subscriptions design. Please ping me on Slack, drop a message in the #graphql channel, or open up a Github issue to discuss!

I would like to investigate generating helpers to make pagination simpler for Connections (based on the Relay Cursor Connections Specification). If you have ideas on this chime in on this thread.

See the full roadmap on Trello.


Author: dillonkearns
Source Code: https://github.com/dillonkearns/elm-graphql
License: View license

#graphql 

A Beginner’s Guide to Setting Up a Web Application with Typescript and Express

Web applications are types of software applications that run on remote servers (source). Examples of web applications can range from word processors, to file scanners, video editing tools, shopping carts, and more. Web applications can be great additions to any website; they can even function as websites themselves (Facebook, Gmail, and Udacity’s classroom are all examples of popular web applications), so understanding how to set up and implement a web application is a fantastic skill to have.

For this guide, I am assuming that you already have a basic knowledge of npmnode and whatExpress Requests and Responses are (or that you at least know what they are used for in their basic sense). Also, I assume that you know what the npm install and mkdir commands do. You have to know basic Typescript to implement — or at least know basic JavaScript to read and understand — the code below. Finally, this is the base for the backend of a web application. You still need to create a frontend application using a framework like Angular or an HTML/CSS file to make requests and display responses.

Before you start, it’s important that you create a folder in your favorite place on your computer. This can be anywhere as long as you have a sense of how you are going to find it later when you come up with an awesome project to start developing.

The Process:

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#web-development #backend #software-development #beginners-guide #beginner

Tia  Gottlieb

Tia Gottlieb

1596336480

Beginners Guide to Machine Learning on GCP

Introduction to Machine Learning

  • Machine Learning is a way to use some set of algorithms to derive predictive analytics from data. It is different than Business Intelligence and Data Analytics in a sense that In BI and Data analytics Businesses make decision based on historical data, but In case of Machine Learning , Businesses predict the future based on the historical data. Example, It’s a difference between what happened to the business vs what will happen to the business.Its like making BI much smarter and scalable so that it can predict future rather than just showing the state of the business.
  • **ML is based on Standard algorithms which are used to create use case specific model based on the data **. For example we can build the model to predict delivery time of the food, or we can build the model to predict the Delinquency rate in Finance business , but to build these model algorithm might be similar but the training would be different.Model training requires tones of examples (data).
  • Basically you train your standard algorithm with your Input data. So algorithms are always same but trained models are different based on use cases. Your trained model will be as good as your data.

ML, AI , Deep learning ? What is the difference?

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ML is type of AI

AI is a discipline , Machine Learning is tool set to achieve AI. DL is type of ML when data is unstructured like image, speech , video etc.

Barrier to Entry Has Fallen

AI & ML was daunting and with high barrier to entry until cloud become more robust and natural AI platform. Entry barrier to AI & ML has fallen significantly due to

  • Increasing availability in data (big data).
  • Increase in sophistication in algorithm.
  • And availability of hardware and software due to cloud computing.

GCP Machine Learning Spectrum

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  • For Data scientist and ML experts , TensorFlow on AI platform is more natural choice since they will build their own custom ML models.
  • But for the users who are not experts will potentially use Cloud AutoML or Pre-trained ready to go model.
  • In case of AutoML we can trained our custom model with Google taking care of much of the operational tasks.
  • Pre-trained models are the one which are already trained with tones of data and ready to be used by users to predict on their test data.

Prebuilt ML Models (No ML Expertise Needed)

  • As discuss earlier , GCP has lot of Prebuilt models that are ready to use to solve common ML task . Such as image classification, Sentiment analysis.
  • Most of the businesses are having many unstructured data sources such as e-mail, logs, web pages, ppt, documents, chat, comments etc.( 90% or more as per various studies)
  • Now to process these unstructured data in the form of text, we should use Cloud Natural Language API.
  • Similarly For common ML problems in the form of speech, video, vision we should use respective Prebuilt models.

#ml-guide-on-gcp #ml-for-beginners-on-gcp #beginner-ml-guide-on-gcp #machine-learning #machine-learning-gcp #deep learning