Flutter Dependency Injection

Dependency Injection

Priority: P1 (HIGH)

Automated class dependency management using get_it and injectable.

Structure

core/injection/
├── injection.dart # Initialization & setup
└── modules/ # Third-party dependency modules (Dio, Storage)

Implementation Guidelines

• Automated Registration: Use @injectable annotations; avoid manual registry calls.
• @LazySingleton: Default for repositories, services, and data sources (init on demand).
• Factory Registration: Use @injectable (Factory) for BLoCs to ensure state resets on every new instance/request. Do NOT use @Singleton() for BLoCs.
• Abstract Injection: Always register implementations as abstract interfaces (as: IService).
• Modules: Use @module for registering third-party instances (e.g., Dio, Hive, SharedPreferences).
• Constructor Injection: Use mandatory constructor parameters; injectable resolves them automatically.
• Test Mocks: Swap implementations in setUp using getIt.unregister() followed by getIt.registerLazySingleton(() => MockService()).

Reference & Examples

For module configuration and initialization templates: See references/REFERENCE.md.

Anti-Patterns

• ❌ getIt<OrderRepository>() inside widget build() — inject via constructor, not GetIt calls in UI
• ❌ @Singleton() on a BLoC — BLoCs must use @injectable (Factory) so state resets per instance
• ❌ Injecting the concrete class: OrderRepositoryImpl repo — always inject the abstract interface
• ❌ getIt.registerLazySingleton<X>(() => X()) in production code — use @injectable annotations; manual registration is only for tests

Related Topics

layer-based-clean-architecture | testing