I was working on a practical project using Angular 8, where I was creating a service and thinking more about how to implement SOLID principles. I decided to have an interface to define my service and a class to implement the logic. Everything was okay with that design, but a question came to my mind, "How can I implement dependency injection with my Angular component?" In this example, I am going to use an abstract class, Let's create an abstract class, named IGreetingsService. This will be used as an Interface with a greeting method. TypeScript x 1 export abstract class IGreetingsService { 2 constructor() { } 3 abstract greeting(): String; 4 } Now, let's create a class, GreetingsServiceImpl. This class implements the IGreetingsService abstract class. TypeScript xxxxxxxxxx 1 1 export class GreetingsServiceImpl implements IGreetingsService { 2 constructor() { } 3 greeting(): String{ 4 return "Pruebaa"; 5 }; 6 } At this point, we have a regular class to use as a service, but we need to add the annotation @Injectable. We have to put it at IGreetingsService. TypeScript x 10 1 @Injectable({ 2 providedIn: 'root', 3 useClass: GreetingsServiceImpl, 4 }) 5 export abstract class IGreetingsService { 6 7 constructor() { } 8 9 abstract greeting(): String; 10 } The magic is at the property useClass. This class is used by the Angular framework to know what concrete class has to use for dependency injection when you are using theIGreetingsService abstract class. So we are ready to use our service into an angular component. TypeScript xxxxxxxxxx 1 12 1 @Component({ 2 selector: 'my-app', 3 templateUrl: './app.component.html', 4 styleUrls: [ './app.component.css' ] 5 }) 6 export class AppComponent { 7 name: String; 8 constructor(private service: IGreetingsService ) { 9 this.name = this.service.greeting(); 10 } 11 12 } At the moment, to create an instance of the AppComponent, Angular automatically creates an instance of GreetingsServiceImpl , instead of IGreetingsService. (Remember IGreetingsService is an abstract class). This approach can help you in several situations; for example, think about a service using REST services to get some data, but now there is a new requirement, and you need to get the same data from session storage or local storage. You can create a new class implementing your abstract class and update the property useClass to refer to your new class. Another situation would be if you needed a different implementation on production environments and testing environments. You can find the complete source code here: https://stackblitz.com/edit/angular8-injectiondependency-interface. A final note, you can define a provider in the component definition annotation to inject a specific implementation of your service. TypeScript x 1 @Component({ 2 selector: 'my-app', 3 templateUrl: './app.component.html', 4 styleUrls: [ './app.component.css' ], 5 providers :[{ provide: IGreetingsService, useClass: GreetingsServiceImpl }] 6 }) Further Reading Angular: Everything You Need to Know [Tutorials]. About Dependency Injection.

In this article, see how to get started using Spring Security to manage authentication and authorization in a Java application.

See ten famous applications that are using React.js nowadays, including Facebook, WhatsApp, and more.

In this article, we provide a brief tutorial on how to remove a BOM character from an Apache Camel exchange message with DSL Java.

This article will explain the method to create an interactive geospatial data visualization with Angular 8, MapboxGL and DeckGL.

In this article, we will be discussing how to test operations in an application that uses a Spring context (with asynchronous operations enabled).

In this article we discuss how to build a REST service that can consume any type of request format, including XML and JSON.

This article demonstrates how you can select an image using the Angular 8 UI, send it to the Spring backend, and retrieve it later from MySQL.

In this article, we discuss how to handle back-button operations with Flutter and webview in order to allow users to navigate between pages.

In this article, we discuss how data binding and server-side rendering differs in both Angular and React.

In this article, we discuss the process of incorporating fault-tolerance into a microservice architecture.

Find out how!

The next step!

In this article, take a look at a tutorial that explains how to write a certain query in Entity Framework.

This article demonstrates how JWTs can be used for securing access to Java microservices built with Spring Boot.

Create a quick Flickr image gallery from scratch with images of varying dimensions using Angular and Bootstrap.

In this article, create Docker images with Jib.

In this article, we discuss how to test asynchronous operations in Spring applications with Spock and Byteman.

The following are 13 of the best React JavaScript frameworks; all are open source. React Native is used for building native applications.

Take a look at how to create a Nexus repository manager using HTTP and how to set up a Docker repository to publish Docker images using the jib plugin.