Dependency Injection

GetIt and injectable for managing dependencies

Dependency injection decouples your code by providing dependencies from outside. GetIt is a popular service locator for Flutter.

Widgets that create their own dependencies are hard to test and tightly coupled. DI inverts the control.

// Tightly coupled (bad)
class UserPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    // Creates its own dependency
    final repo = ApiUserRepository();
    // Can't swap for testing
  }
}

// Dependency injected (good)
class UserPage extends StatelessWidget {
  final UserRepository repo;
  UserPage({required this.repo});
  // Can be API, fake, or mock
}

Service Container

ApiClientSingleton

AuthServiceLazy

depends on: ApiClient

UserRepoFactory

depends on: ApiClient

PostRepoFactory

depends on: ApiClient

UserBlocFactory

depends on: UserRepo

33 / 35