Services and dependency injection

Stefano Di Cecco
2 min readDec 28, 2022

Services and dependency injection are important concepts in Angular that allow you to design modular and reusable code for your application. In this article, we’ll take a closer look at what services and dependency injection are, and how you can use them to build scalable and maintainable applications in Angular.

First, let’s define what we mean by services and dependency injection. A service is a class that provides a set of related functions or features that can be used across your application. Services are a way to encapsulate logic and provide a clean separation of concerns between different parts of your application.

Dependency injection is a pattern that allows you to inject or pass an instance of a service into a component or another service, rather than creating the service directly within the component or service. This allows you to centralize the creation and management of services in a single location, and make it easier to reuse and test your code.

In Angular, you can use the @Injectable decorator to create a service, and the @Inject decorator to inject the service into a component or another service. Here’s an example of a simple service in Angular:

import { Injectable } from '@angular/core';
@Injectable({
providedIn: 'root'
})
export class DataService {
constructor() {}
getData() {
return [1, 2, 3, 4, 5];
}
}

In this example, we’ve created a service called DataService that provides a simple getData function that returns an array of numbers. The @Injectable decorator specifies that the service can be injected into other components or services.

Now let’s look at how you can inject the DataService into a component. Here’s an example of a component that uses the DataService:

import { Component } from '@angular/core';
import { DataService } from './data.service';
@Component({
selector: 'app-root',
template: `
<h1>Data: {{data}}</h1>
`
})
export class AppComponent {
data: any;
constructor(private dataService: DataService) {
this.data = dataService.getData();
}
}

In this example, we’ve injected the DataService into the AppComponent using the constructor. We’ve also used the private keyword to create a property called dataService that holds the injected instance of the DataService. We can then use the dataService property to call the getData function and retrieve the data that we want to display in the component’s template.

Services and dependency injection are essential tools in Angular that allow you to design modular and reusable code for your application. By creating services and injecting them into your components and other services, you can build scalable and maintainable applications that are easy to test and maintain.

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Stefano Di Cecco

Self-motivated IT professional with great knowledge and proficiency in JavaScript, TypeScript. Expertise in frameworks like React.js, Angular.