Services

In Angular, a service is a class that encapsulates a specific functionality or feature and provides it to other parts of the application through a well-defined API. Services are typically used to encapsulate logic that is not directly related to the view or the component, such as data access, validation, and business logic.

There are several benefits to using services in Angular:

1. Reusability: Services can be used by multiple components in an application, making the code more reusable and easier to maintain.
2. Separation of concerns: Services help to separate the logic of an application into distinct layers, making it easier to understand and maintain the codebase.
3. Testing: Services can be easily tested in isolation, without having to rely on the component or other parts of the application.
4. Shared State: Services can be used to share state between multiple components, which is crucial for a complex application.

There are two main types of services in Angular,

1. In-memory services, which are typically used during development and testing, and
2. Backend services, which are used to connect to a remote server to retrieve or update data.

Creating a service in Angular is straightforward, you can generate it by running the command ”ng generate service <service-name>” or you can create it manually. Here’s an example of a simple service:

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

@Injectable({
  providedIn: 'root'
})
export class MyService {

  constructor() { }

  sayHello(): string {
    return 'Hello';
  }
}

This service can be then imported and used in any component where it is needed, Here’s an example of how to use the service in a component:

import { Component } from '@angular/core';
import { MyService } from './my.service';

@Component({
  selector: 'app-root',
  template: `
    <h1>{{message}}</h1>
  `
})
export class AppComponent {
  message: string;

  constructor(private myService: MyService) {
    this.message = this.myService.sayHello();
  }
}

In addition to standard services, Angular also provides several built-in services such as:

• HttpClient: a service for making HTTP requests to a remote server.
• Router: a service for managing the application’s routing and navigation.
• ActivatedRoute: a service for interacting with the current route.
• FormsModule : a service for working with forms.

It is common practice to use services to encapsulate non-view related logic in Angular applications, this will help you keep the application maintainable, easy to understand and easy to test.