Dependency Injection (DI) is a core concept in Angular that enables loose coupling and testability in applications. By injecting dependencies into components, you promote modular design and maintainability. Here's a breakdown:

Key Concepts

  • Services in Angular are classes that provide functionalities (e.g., data access, utilities) to other classes via DI.
    Angular_Service
  • DI in Angular works through the dependency injection module (DI module), which manages object creation and injection.
    Dependency_Injection
  • Providers define how dependencies are created and injected, often in the @Injectable() decorator.
    Providers_Angular

Best Practices

  • Use @Injectable() for services that need to be injected.
  • Favor constructor injection for clarity and testability.
  • Avoid direct instantiation of services in components.

Example Code

// Service definition
@Injectable({
  providedIn: 'root'
})
export class DataService {
  getData(): string {
    return 'Sample data from service';
  }
}

// Component using the service
constructor(private dataService: DataService) {}

ngOnInit() {
  console.log(this.dataService.getData()); // Access service via DI
}

Benefits

  • ✅ Reusability: Services can be shared across components.
  • ✅ Maintainability: Decouples logic, making updates easier.
  • ✅ Testability: Mock dependencies for unit testing.

For a deeper dive into DI in Angular, check out our Dependency Injection Tutorial. 🚀