Introducing BLoC Pattern with React and RxJS

Introducing BLoC Pattern with React and RxJS - As we saw, RxJS is a library for reactive programming using Observables, to make it easier to compose asynchronous or callback-based code…

Hello! Have you already heard about BLoC Pattern? BLoC Pattern was announced by Paolo Soares in the Google Dart Conference 2018. Since then, it’s usual to hear about this pattern linked with Flutter, as an alternative way to do state management. That’s because the initial proposal was to reuse the code related to the business logic in different platforms, in this case, Angular Dart and Flutter. But now let’s try to bring these concepts to React and JS environment, and think how it can be useful, for example, in the reuse of the code between React and React-Native applications.

First of all, let’s see a little bit about RxJS before introducing the pattern.

Reactive Programming with RxJS

ReactiveX combines the Observer pattern with the Iterator pattern and functional programming with collections to fill the need for an ideal way of managing sequences of events. Here we are going to see especially these 3 concepts:

• Observable: represents the idea of an invokable collection of future values or events.
• Observer: is a collection of callbacks that knows how to listen to values delivered by the Observable.
• Subject: is a special type of Observable that allows values to be multicasted to many Observers.

Every Subject is an Observable. Given a Subject, you can to it, providing an Observer, which will start receiving values normally. Now let’s see the usage of the Subject class and others which extends from it. So let’s start from the beginning:

Subject:

That’s the usage of a simple Subject object. We created the Subject and we subscribed a function as Observer which will print the data when the Subject receives a new value. Then we feed the subject with the values 1 and 2. The expected output is Value 1 and Value 2.

const rxjs = require("rxjs");
const subject = new rxjs.Subject();
subject.subscribe(function(v){
    console.log(`Value ${v}`);
});
subject.next(1);
subject.next(2);
//output is:
//Value 1
//Value 2

BehaviorSubject:

One of the variants of Subjects is the BehaviorSubject, which has a notion of “the current value”. It stores the latest value emitted to its consumers, and whenever a new Observer subscribes, it will immediately receive the “current value” from the BehaviorSubject. Also, it possibilities we initialize our Subject with an initial value. Let’s see:

const rxjs = require("rxjs");
const subject = new rxjs.BehaviorSubject(0);
subject.subscribe(function(v){
   console.log(`Observer A ${v}`);
});
subject.next(1);
subject.next(2);
subject.subscribe(function(v){
   console.log(`Observer B ${v}`);
});
subject.next(3);
//output is:
//Observer A 0
//Observer A 1
//Observer A 2
//Observer B 2
//Observer A 3
//Observer B 3

ReplaySubject:

A ReaplaySubject is similar to a BehaviorSubject in that it can send old values to new subscribers, but it can also record a part of the Observable execution. Also, it possibilities we initialize our Subject saying how much values we wanted to be recorded. In other words, we can specify how many values to replay. Let’s see:

const rxjs = require("rxjs");
const subject = new rxjs.ReplaySubject(2); //Buffer with size 2
subject.subscribe(function(v){
   console.log(`Observer A ${v}`);
});
subject.next(1);
subject.next(2);
subject.next(3);
subject.subscribe(function(v){
   console.log(`Observer B ${v}`);
});
//output is:
//Observer A 1
//Observer A 2
//Observer A 3
//Observer B 2
//Observer B 3

Now let’s figure out what the BLoC Pattern has to offer to us, and how can we use it with RxJS.

BLoC Pattern

What the BLoC(Bussiness Logic Component) seeks for, is take all business logic code off the UI, and using it only in the BLoC classes. It brings to the project and code, independence of environment and platform, besides put the responsibilities in the correct component. This pattern is all based on Reactive Programming, because of it, we are going to use the RxJS library. As we saw, RxJS is a library for reactive programming using Observables, to make it easier to compose asynchronous or callback-based code.

All communication between the UI (React Components) and BLoC Classes (JS Classes) can be only be done between the Observables. That’s why we are going to use the Subjects classes, which extends from Observables.

https://www.didierboelens.com/2018/08/reactive-programming—streams—bloc/ (Adapted)

Looking at the architecture we can see that:

• Components send data/event (value) to the BLoC via Subjects.
• Components are notified by the BLoC via subscription.
• The business logic which is implemented by the BLoC is none of their concern.

From this statement, we can directly see a huge benefit. We may change the Business Logic at any time, with a minimal impact on the application. And see that there’s no business logic in the component, that means what happened in BLoC is not the concern of UI. This architecture improves even easier tests, in which the business logic tests cases needed to be applied only to the BLoC classes.

Now let’s see it in practice

With all concepts showed before you can already build your React application applying the BLoC Patter. But you’ll still need to deal with state management because the Subject subscription will be directly attached to your component. Because of that, I created a component called BlocBuilder which renders itself based on the latest snapshot emitted by a Subject and will help us to implement the pattern focusing on main principles.

What do we want?

https://wiltonribeiro.github.io/bloc-react-example/

Let’s create a simple counter page with increment, decrement functions, and an error handler. Just to practice what we saw until here.

BLoC Class

We are going to create our first BLoC class. The class will be responsible to carry all subjects related to the Business Logic which the class is responsible, in this case, to counter.

//importing the rxjs library
	import * as rxjs from 'rxjs';
	

	class CounterBloc {
	

	    constructor(){
	        //creating our BehaviorSubject with initial value of 0
	        this.counterSubject = new rxjs.BehaviorSubject(0);
	    }
	

	    //an increment function that deals with the subject
	    increment = () =>{
	        let count = this.counterSubject.getValue() + 1;
	        this.counterSubject.next(count);
	    };
	

	    //a decrement function that deals with the subject
	    decrement = () => {
	        let count = this.counterSubject.getValue() - 1;
	        this.counterSubject.next(count);
	    };
	

	    //the error function with deal with sending an error through the subject
	    error = () => {
	        this.counterSubject.error("An error simulation");
	    };
	

	    //the get function to return the subject. It allows the component to subscribe as Observer.
	    getCounterSubject = () => {
	        return this.counterSubject;
	    };
	

	}
	

	export default CounterBloc;

This app example is pretty simple. But imagine if this app was bigger and that’s one of BLoC classes that you was working hard. But now the requirement has been changed and the increment function needs to add two at time. Do you agree with me (that in this case) a requirement changing in the business logic shouldn’t affect UI code, right? If yes, great! You got it, that is the point to separate responsibilities. So if it happens only the BLoC classes will be updated without any impact in the UI code.

UI Component

Our UI Component is responsible for initializing our BLoC class, then pass it through parameter to the BlocBuilder. What happens is:

import React from 'react';
	import logo from './logo.svg';
	import './App.css';
	

	//importing the BlocBuilder
	import BlocBuilder from "bloc-builder-react";
	

	//importing our CounterBloc
	import CounterBloc from "./bloc/CounterBloc";
	

	class App extends React.Component {
	

	  constructor(props){
	    super(props);
	    
	    //initializes the CounterBloc
	    this.bloc = new CounterBloc();
	    
	  }
	

	  render() {
	    return (
	        <div className="App">
	          <header className="App-header">
	

	            <img src={logo} className="App-logo" alt="logo" />
	      
	            //using BlocBuilder to render based always on the latest snapshot emitted by a Subject
	            <BlocBuilder
	                //setting to the BlocBuilder our Subject
	                subject = {this.bloc.getCounterSubject()}
	                //builder function that will render our JSX when the subject receives a new value
	                builder = {(snapshot) => {
	                  //if that's not an error, let's render a div with de value of the snapshot
	                  switch (!snapshot.error) {
	                    case true:
	                      return (
	                          <div> The count has the current value of {snapshot.data}</div>
	                      );
	                    //else let's expose the error
	                    default :
	                      return (<div>Error : <code>{snapshot.error}</code></div>);
	                  }
	                }}
	            />
	

	            <div className="App-buttons">
	                //setting Bloc functions to the properly buttons
	                <button onClick={this.bloc.increment}>Incriment</button>
	                <button onClick={this.bloc.decrement}>Decrement</button>
	                <button onClick={this.bloc.error}>Simulate error</button>
	            </div>
	

	          </header>
	        </div>
	    );
	  }
	}
	

	export default App;

Flux

• In the render function. When the BlocBuilder subscribes as an observer of our counterSubject, as a BehaviorSubject, it catches his initialization value. Then it renders the builder JSX, containing the full text exposing the counter as 0.
• When someone clicks on the button to increment, it calls our bloc method to increment. Our bloc class gets the last value from our counterSubject, add one and feed our subject with the new value.
• Then our BlocBuilder as an observer will render itself again, but now exposing the full text with the value 1.
• The same as above happens to the decrement function.
• When someone clicks on the error function, our bloc will send an error message to the subject.
• Then our BlocBuilder as an observer will render itself again but now will check that some error has been happened and will expose a message with the error.

Notes

And that’s it. The pattern seeks to separate the responsibilities and put them in the right place. And more, the use of reactive programming can provide a great way to make the state management of your app much more simple. Using this pattern you can, for example, make components indirectly communicate with others just through the same BLoC Class. Suppose a *SliderShowBloc, *for example, it can be the bridge between a reactive communication between your Slider Banner Component and the Slider Buttons Component.

When all business logic code is the BLoC Classes, you can just reuse your code to any platform which accepts the same programming language. In this case, it can be useful to reuse code in the implementation of a Web App with React and a Mobile App with React Native.

#reactjs #flutter

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How native is React Native? | React Native vs Native App Development

If you are undertaking a mobile app development for your start-up or enterprise, you are likely wondering whether to use React Native. As a popular development framework, React Native helps you to develop near-native mobile apps. However, you are probably also wondering how close you can get to a native app by using React Native. How native is React Native?

In the article, we discuss the similarities between native mobile development and development using React Native. We also touch upon where they differ and how to bridge the gaps. Read on.

A brief introduction to React Native

Let’s briefly set the context first. We will briefly touch upon what React Native is and how it differs from earlier hybrid frameworks.

React Native is a popular JavaScript framework that Facebook has created. You can use this open-source framework to code natively rendering Android and iOS mobile apps. You can use it to develop web apps too.

Facebook has developed React Native based on React, its JavaScript library. The first release of React Native came in March 2015. At the time of writing this article, the latest stable release of React Native is 0.62.0, and it was released in March 2020.

Although relatively new, React Native has acquired a high degree of popularity. The “Stack Overflow Developer Survey 2019” report identifies it as the 8th most loved framework. Facebook, Walmart, and Bloomberg are some of the top companies that use React Native.

The popularity of React Native comes from its advantages. Some of its advantages are as follows:

• Performance: It delivers optimal performance.
• Cross-platform development: You can develop both Android and iOS apps with it. The reuse of code expedites development and reduces costs.
• UI design: React Native enables you to design simple and responsive UI for your mobile app.
• 3rd party plugins: This framework supports 3rd party plugins.
• Developer community: A vibrant community of developers support React Native.

Why React Native is fundamentally different from earlier hybrid frameworks

Are you wondering whether React Native is just another of those hybrid frameworks like Ionic or Cordova? It’s not! React Native is fundamentally different from these earlier hybrid frameworks.

React Native is very close to native. Consider the following aspects as described on the React Native website:

• Access to many native platforms features: The primitives of React Native render to native platform UI. This means that your React Native app will use many native platform APIs as native apps would do.
• Near-native user experience: React Native provides several native components, and these are platform agnostic.
• The ease of accessing native APIs: React Native uses a declarative UI paradigm. This enables React Native to interact easily with native platform APIs since React Native wraps existing native code.

Due to these factors, React Native offers many more advantages compared to those earlier hybrid frameworks. We now review them.

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How to Select and Hire the Best React JS and React Native Developers?

Since March 2020 reached 556 million monthly downloads have increased, It shows that React JS has been steadily growing. React.js also provides a desirable amount of pliancy and efficiency for developing innovative solutions with interactive user interfaces. It’s no surprise that an increasing number of businesses are adopting this technology. How do you select and recruit React.js developers who will propel your project forward? How much does a React developer make? We’ll bring you here all the details you need.

What is React.js?

Facebook built and maintains React.js, an open-source JavaScript library for designing development tools. React.js is used to create single-page applications (SPAs) that can be used in conjunction with React Native to develop native cross-platform apps.

React vs React Native

• React Native is a platform that uses a collection of mobile-specific components provided by the React kit, while React.js is a JavaScript-based library.
• React.js and React Native have similar syntax and workflows, but their implementation is quite different.
• React Native is designed to create native mobile apps that are distinct from those created in Objective-C or Java. React, on the other hand, can be used to develop web apps, hybrid and mobile & desktop applications.
• React Native, in essence, takes the same conceptual UI cornerstones as standard iOS and Android apps and assembles them using React.js syntax to create a rich mobile experience.

What is the Average React Developer Salary?

In the United States, the average React developer salary is $94,205 a year, or $30-$48 per hour, This is one of the highest among JavaScript developers. The starting salary for junior React.js developers is $60,510 per year, rising to $112,480 for senior roles.

* React.js Developer Salary by Country

• United States- $120,000
• Canada - $110,000
• United Kingdom - $71,820
• The Netherlands $49,095
• Spain - $35,423.00
• France - $44,284
• Ukraine - $28,990
• India - $9,843
• Sweden - $55,173
• Singapore - $43,801

In context of software developer wage rates, the United States continues to lead. In high-tech cities like San Francisco and New York, average React developer salaries will hit $98K and $114per year, overall.

However, the need for React.js and React Native developer is outpacing local labour markets. As a result, many businesses have difficulty locating and recruiting them locally.

It’s no surprise that for US and European companies looking for professional and budget engineers, offshore regions like India are becoming especially interesting. This area has a large number of app development companies, a good rate with quality, and a good pool of React.js front-end developers.

As per Linkedin, the country’s IT industry employs over a million React specialists. Furthermore, for the same or less money than hiring a React.js programmer locally, you may recruit someone with much expertise and a broader technical stack.

How to Hire React.js Developers?

• Conduct thorough candidate research, including portfolios and areas of expertise.
• Before you sit down with your interviewing panel, do some homework.
• Examine the final outcome and hire the ideal candidate.

Why is React.js Popular?

React is a very strong framework. React.js makes use of a powerful synchronization method known as Virtual DOM, which compares the current page architecture to the expected page architecture and updates the appropriate components as long as the user input.

React is scalable. it utilises a single language, For server-client side, and mobile platform.

React is steady.React.js is completely adaptable, which means it seldom, if ever, updates the user interface. This enables legacy projects to be updated to the most new edition of React.js without having to change the codebase or make a few small changes.

React is adaptable. It can be conveniently paired with various state administrators (e.g., Redux, Flux, Alt or Reflux) and can be used to implement a number of architectural patterns.

Is there a market for React.js programmers?
The need for React.js developers is rising at an unparalleled rate. React.js is currently used by over one million websites around the world. React is used by Fortune 400+ businesses and popular companies such as Facebook, Twitter, Glassdoor and Cloudflare.

Final thoughts:

As you’ve seen, locating and Hire React js Developer and Hire React Native developer is a difficult challenge. You will have less challenges selecting the correct fit for your projects if you identify growing offshore locations (e.g. India) and take into consideration the details above.

If you want to make this process easier, You can visit our website for more, or else to write a email, we’ll help you to finding top rated React.js and React Native developers easier and with strives to create this operation

#hire-react-js-developer #hire-react-native-developer #react #react-native #react-js #hire-react-js-programmer

What are hooks in React JS? - INFO AT ONE

In this article, you will learn what are hooks in React JS? and when to use react hooks? React JS is developed by Facebook in the year 2013. There are many students and the new developers who have confusion between react and hooks in react. Well, it is not different, react is a programming language and hooks is a function which is used in react programming language.
Read More:- https://infoatone.com/what-are-hooks-in-react-js/

#react #hooks in react #react hooks example #react js projects for beginners #what are hooks in react js? #when to use react hooks

React 18: Things You Need To Know About React JS Latest Version

The most awaited version of React 18 is finally out now. Its team has finally revealed the alpha version of React 18 and its plan, though the official launch is still pending. This time the team has tried something and released the plan first to know their user feedback because the last version of React 17 was not that much appreciated among developers.

According to Front-end Frameworks Survey, React JS has ranked top in the list of most loved frameworks. Thus, the developer communities expect a bit higher from the framework, so they are less appreciative of the previous launch.
So, this time React 18 will be a blast. For beginners, the team is working on a new approach. They have called a panel of experts, library authors, educators, and developers to take part in a working group. Initially, it will be a small group.

I am not a part of this release but following the team on their GitHub discussion group. After gathering the information from there, I can say that they have planned much better this time.

React 17 was not able to meet the developer's community. The focus was all primarily centered on making it easier to upgrade React itself. React 18 release will be the opposite. It has a lot of features for react developers.

Read more here: React 18: Things You Need To Know About React JS Latest Version

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Build a simple React Native Pokemon app with React-Navigation

As we start learning new technologies we want to start building something or work on a simple project to get a better understanding of the technology. So, let’s build this simple app.
For this app, we will be using PokeApi to get our pokemon data, and also we will be using Hooks. I am using pokemondb for pokemon sprites. It’s just a personal preference you can use whatever you want.

#react-native #react-native-app #react-navigation #react-native-development #react