Angular Services

Version: Angular 21 (2025) Tags: Services, @Injectable, DI

References: Services Guide • @Injectable API

Best Practices

• Create service with providedIn

@Injectable({ providedIn: 'root' })
export class DataService {
  getData() {
    return this.http.get('/api/data');
  }
}

• Use inject() function

@Injectable({ providedIn: 'root' })
export class UserService {
  private http = inject(HttpClient);
  
  getUsers() {
    return this.http.get<User[]>('/api/users');
  }
}

• Use factory providers

@Injectable({
  providedIn: 'root',
  useFactory: () => new LoggerService(environment.production)
})
export class LoggerService {
  constructor(private isProduction: boolean) {}
}

• Use providedIn: 'any' for lazy services

@Injectable({ providedIn: 'any' })
export class LazyService {}

• Use service in component

@Component({})
export class MyComponent {
  private dataService = inject(DataService);
  
  data$ = this.dataService.getData();
}

• Use multiple services

@Component({})
export class MyComponent {
  private auth = inject(AuthService);
  private http = inject(HttpClient);
  private router = inject(Router);
}

• Use service for shared state

@Injectable({ providedIn: 'root' })
export class CartService {
  private items = signal<Item[]>([]);
  
  cartItems = this.items.asReadonly();
  
  addItem(item: Item) {
    this.items.update(items => [...items, item]);
  }
}