In-depth Guides
Dependency Injection

Creating and using services

Services are reusable pieces of code that can be shared across your Angular application. They typically handle data fetching, business logic, or other functionality that multiple components need to access.

Creating a service

You can create a service with the Angular CLI with the following command:

ng generate service CUSTOM_NAME

This creates a dedicated CUSTOM_NAME.ts file in your src directory.

You can also manually create a service by adding the @Injectable() decorator to a TypeScript class. This tells Angular that the service can be injected as a dependency.

Here is an example of a service that allows users to add and request data:

// 📄 src/app/basic-data-store.tsimport { Injectable } from '@angular/core';@Injectable({ providedIn: 'root' })export class BasicDataStore {  private data: string[] = []  addData(item: string): void {   this.data.push(item)  }  getData(): string[] {    return [...this.data]  }}

How services become available

When you use @Injectable({ providedIn: 'root' }) in your service, Angular:

  • Creates a single instance (singleton) for your entire application
  • Makes it available everywhere without any additional configuration
  • Enables tree-shaking so the service is only included in your JavaScript bundle if it's actually used

This is the recommended approach for most services.

Injecting a service

Once you've created a service with providedIn: 'root', you can inject it anywhere in your application using the inject() function from @angular/core.

Injecting into a component 

import { Component, inject } from '@angular/core';import { BasicDataStore } from './basic-data-store';@Component({  selector: 'app-example',  template: `    <div>      <p>{{ dataStore.getData() }}</p>      <button (click)="dataStore.addData('More data')">        Add more data      </button>    </div>  `})export class ExampleComponent {  dataStore = inject(BasicDataStore);}

Injecting into another service 

import { inject, Injectable } from '@angular/core';import { AdvancedDataStore } from './advanced-data-store';@Injectable({  providedIn: 'root',})export class BasicDataStore {  private advancedDataStore = inject(AdvancedDataStore);  private data: string[] = [];  addData(item: string): void {    this.data.push(item);  }  getData(): string[] {    return [...this.data, ...this.advancedDataStore.getData()];  }}

Next steps

While providedIn: 'root' covers most use cases, Angular offers additional ways to provide services for specialized scenarios:

  • Component-specific instances - When components need their own isolated service instances
  • Manual configuration - For services that require runtime configuration
  • Factory providers - For dynamic service creation based on runtime conditions
  • Value providers - For providing configuration objects or constants

You can learn more about these advanced patterns in the next guide: defining dependency providers.