All About Angular

Angular is a popular front-end development framework built on top of TypeScript, which is a superset of JavaScript. It allows developers to build powerful, dynamic, and scalable web applications with ease. One of the unique features of Angular is its hook lifecycle, which provides a way for developers to react to events during the component's lifetime. In this blog, we will explore what Angular is, its 8 hook lifecycle methods, important features, and how to create an Angular project with an example.

What is Angular?

Angular is a TypeScript-based open-source front-end development framework used to build web applications. It was developed by Google and is now maintained by a large community of developers. Angular uses a component-based architecture, which allows developers to create reusable and modular components that can be easily integrated into an application. Angular also provides a powerful set of tools, such as dependency injection, forms, and routing, to simplify the development process.

Hook Lifecycle in Angular:

Angular components have a lifecycle that goes through various stages, from creation to destruction. During each stage, Angular provides hooks that allow developers to react to events and perform specific actions. Here are the different hooks available in Angular:

1. constructor: This is called first and initializes the component.

2. ngOnChange(): This hook is called when the input properties of a component change.

3. ngOnInit(): This hook is called when the component is initialized.

4. ngDoCheck(): This hook is called during every change detection cycle.

5. ngAfterContentInit(): This hook is called after the component's content has been initialized.

6. ngAfterContentChecked(): This hook is called after the component's content has been checked.

7. ngAfterViewInit(): This hook is called after the component's view has been initialized.

8. ngAfterViewChecked(): This hook is called after the component's view has been checked.

9. ngOnDestroy(): This hook is called just before the component is destroyed.

Important Features of Angular

1.Component Data binding

Components are the basic building blocks of Angular applications. They define the user interface and the logic behind it. Data binding allows us to synchronize data between the component and its template, so any changes in the component will automatically reflect in the template and vice versa,

There are four types of Data Binding in Angular:

· Interpolation: It allows us to display the value of a component property in the template by using double curly braces {{}}

· Property Binding: It allows us to set the value of an HTML element property using a component property by using square brackets []

· Event Binding: It allows us to listen for and respond to events from HTML elements in the template by using parentheses ( ).

· Two-Way Binding: It allows us to bind a component property to an input element and listen for changes to that element using NgModule.

2.Directives :

Directives are instructions that can be attached to an HTML element to manipulate its behavior and appearance. There are two types of directives in Angular: structural directives and attribute directives.

3.Services & Dependency Injection :

Services are a way to share data and functionality across different components in an Angular application. Dependency injection is a technique for obtaining instances of these services and injecting them into the components that need them.

4.Routing :

Routing allows us to navigate between different views or pages in an Angular application. We define routes for different views and specify which component to load when the user navigates to that route.

5.Observables:

Observables are a way of handling asynchronous operations in Angular. They are used to handle events, perform network requests, and perform other types of asynchronous operations. An observable is essentially a stream of values that can be subscribed to by observers. Observables can emit values over time, or they can emit a single value and then complete.

6.Forms

Angular provides a powerful and flexible way to handle forms. There are two types of forms in Angular: Template-Driven Forms(the simplest way to handle forms in Angular. They rely on two-way data binding to keep the form data and the view in sync. Template-driven forms are easy to use and require less boilerplate code) and Reactive Forms(forms provide more control and flexibility than template-driven forms. They are created programmatically using the FormBuilder service, and they rely on reactive programming concepts like Observables and RxJS).

7.Pipes :

Pipes an important feature of Angular that allow you to transform data before displaying it in the template. Pipes can be used to format data, filter data, sort data, and more. Angular comes with several built-in pipes, such as the date pipe and the currency pipe, and you can also create your own custom pipes.

8.Http:

Angular is used to perform HTTP requests and handle responses. You can use it to interact with web servers and APIs, and to fetch and save data from database.

Some of the most important files in Angular Projects are:

1. package.json: This file lists the dependencies that the application needs to run, as well as any scripts that can be used to build, test, or run the application.

2. angular.json: This file provides configuration settings for the Angular CLI, such as build options and project settings.

3. tsconfig.json: This file contains TypeScript compiler options for the project.

4. index.html: This file is the main HTML file for the application, and contains the root component tag (<app-root>).

5. main.ts: This file is the entry point for the application and bootstraps the root module of the application.

6. app.module.ts: This file defines the root module for the application, which is responsible for importing and configuring all the necessary modules, components, and services that the application needs.

7. app.component.ts: This file defines the root component for the application, which is responsible for rendering the overall layout and structure of the application.

8. app-routing.module.ts: This file defines the routes for the application, which determine which component to display based on the URL path.

9. *.component.ts: These files define individual components that are used to build the features and functionality of the application.

10. *.service.ts: These files define services that are used to provide data and functionality to different parts of the application.

Overall, these files work together to provide the structure and functionality of an Angular application. The package.json, angular.json, and tsconfig.json files provide configuration and build options for the application, while the index.html, main.ts, and app.module.ts files define the basic structure of the application. The app.component.ts and app-routing.module.ts files define the root component and routing for the application, respectively, and the *.component.ts and *.service.ts files define the individual components and services that provide the features and functionality of the Steps to create an Angular Application:

Steps to Create an Angular Application:

Step 1: Install Angular CLI

First, make sure you have the Angular CLI installed. You can install it globally using the following command:

npm install -g @angular/cli

Step 2: Create a new Angular project in Visual studio.

Create a new Angular project using the Angular CLI:

ng new my-angular-app

This will create a new Angular project with the default settings.

Step 3: Create a user model

Create a new file called user.ts in the src/app directory and this will define the structure of a user object that we'll be using in our application.

Example:

export interface User { id: number; name: string; email: string}

Step 4: Create a new Angular component.

Run the following command in your terminal to create a new component:

ng generate component component-name

Example:

ng g c user-list

This will create a new component called user-list in the src/app directory.

Step 5: Implement the component

In this code, we're creating a new UserListComponent class(the user-list.component.ts file) with a users property and a UserService dependency. In the ngOnInit method, we're using the getUsers method from the UserService to retrieve a list of users from the backend API and assign them to the users property.

Example:

import { Component, OnInit } from '@angular/core'; import { UserService } from '../user.service'; import { User } from '../user'; @Component({ selector: 'app-user-list', templateUrl: './user-list.component.html', styleUrls: ['./user-list.component.css'], }) export class UserListComponent implements OnInit { users: User[] = []; constructor(private userService: UserService) {} ngOnInit() { this.userService.getUsers().subscribe((users) => { this.users = users; }); }

Step 6: Create a new Angular service

Services in Angular are used to provide data to components. In this step, we'll create a new service to interact with the Spring Boot backend API.

Run the following command in your terminal to create a new service:

ng generate service service-name

Example:

ng g s user

This will create a new service called user in the src/app directory.

Step 7: Implement the service

Example

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

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

@Injectable({ providedIn: 'root', })

export class UserService {

private apiUrl = 'http://localhost:8080/users';

constructor(private http: HttpClient) {}

getUsers() { return this.http.get(this.apiUrl); }

Step 8: Create a new Angular template

In this code, we're creating a new UserService class with methods to perform CRUD operations. We're using Angular's HttpClient module to send HTTP requests to the backend API.

Example

<table> <thead> <tr> <th>ID</th> <th>Name</th> <th>Email</th> <th>Actions</th> </tr> </thead> <tbody> <tr *ngFor="let user of users"> <td>{{ user.id }}</td> <td>{{ user.name }}</td> <td>{{ user.email }}</td> <td> <button (click)="editUser(user)">Edit</button> <button (click)="deleteUser(user.id)">Delete</button> </td> </tr> </tbody> </table>

Step 9: app-module.ts

We have to include the UserList Component in the app-module.

Example:

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

import { BrowserModule } from '@angular/platform-browser';

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

import { UserListComponent } from './user-list/user-list.component';

@NgModule({

declarations: [

AppComponent,

UserListComponent

],

imports: [

BrowserModule

],

providers: [],

bootstrap: [AppComponent]

})

export class AppModule { }

Step 10: app-component.ts

The root app-component is loaded and displayed in the browser, along with any child components it contains.

Example:

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

@Component({

selector: 'app-root', templateUrl: './app.component.html',

styleUrls: ['./app.component.css'] })

export class AppComponent {

title = 'My Angular App';

}

Step 11: app-routing.module.ts

Angular's built-in router makes it easy to create multiple views within a single-page application. Developers can define routes for each view, and Angular will handle navigation between them.

Example:

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

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

import { UsersComponent } from './users.component';

const routes: Routes = [{ path: 'users', component: UsersComponent }, ];

@NgModule({

imports: [RouterModule.forRoot(routes)],

exports: [RouterModule], }) export class AppRoutingModule {}

Step 12: Run the server

ng s

This is the basic flow of angular for creating a project .Overall, Angular is a powerful tool for building modern web applications.