Building Modular Flutter Apps with the Feature-Driven Architecture Pattern

Introduction

In modern mobile development, scaling a Flutter app often leads to tangled dependencies and unpredictable build times. The Feature-Driven Architecture pattern addresses this by dividing your app into self-contained feature modules. Each module handles its own data, domain, and UI layers, making development parallelizable, testable, and maintainable. In this tutorial, you’ll learn how to build a modular Flutter project with clear boundaries between core logic and feature implementations.

Setting Up a Feature-Driven Architecture

Start by organizing your repository into a core/ directory and a features/ directory. The core contains shared services, utilities, and abstractions. Inside features/, each feature gets its own folder.

Project root:

Initialize your pubspec.yaml to only include common dependencies in the root. Feature-specific plugins live in the app-level pubspec to avoid cross-feature coupling.

Organizing Feature Modules

Within each feature folder, apply a layered structure:

features/auth/ 
├── data/          // Repositories, data sources
├── domain/        // Entities, use cases
└── presentation/  // Widgets, BLoC or Provider classes

Keep imports internal to a feature. Expose a single Dart file (e.g., auth_module.dart) that exports the public interface:

// features/auth/auth_module.dart
export 'data/auth_repository.dart';
export 'domain/login_usecase.dart';
export 'presentation/login_page.dart';

This isolates consumers from implementation details.

Sharing Core and Utilities

Place shared services in core/: logging, network, error handling, and DI setup:

// core/di.dart
import 'package:get_it/get_it.dart';
import 'network_service.dart';

final GetIt di = GetIt.instance;

void initCoreDependencies() {
  di.registerLazySingleton<NetworkService>(() => NetworkService());
}

Each feature can register its own dependencies separately by supplying a FeatureModule initializer for easy testing and dynamic loading.

Implementing Navigation and Dependencies

Use a routing package (e.g., go_router) to register feature routes. Delegate the route definitions to each module:

// features/profile/profile_routes.dart
import 'package:go_router/go_router.dart';
import 'presentation/profile_page.dart';

List<GoRoute> profileRoutes = [
  GoRoute(
    path: '/profile',
    builder: (_, __) => ProfilePage(),
  ),
];

In your main app:

// main.dart
import 'core/di.dart';
import 'features/profile/profile_routes.dart';
import 'package:go_router/go_router.dart';

void main() {
  initCoreDependencies();
  final router = GoRouter(routes: [...profileRoutes, ...authRoutes]);
  runApp(App(router: router));
}

Each feature also wires up its own DI in an initFeature() function, isolating service registration and avoiding global dependency bloat.

Testing Feature Modules

Because features are decoupled, you can write targeted tests:

• Unit tests for domain logic (use cases, value objects).

• Repository tests with mocked data sources.

• Widget tests for presentation components using WidgetTester.

Example unit test for a login use case:

// features/auth/domain/login_usecase_test.dart
import 'package:flutter_test/flutter_test.dart';
import 'login_usecase.dart';

void main() {
  test('LoginUseCase returns token on valid creds', () async {
    final useCase = LoginUseCase(mockRepo);
    final result = await useCase.execute('user', 'pass');
    expect(result.isSuccess, true);
  });
}

Run flutter test per feature folder or set up CI to isolate test suites.

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Conclusion

By adopting Feature-Driven Architecture in your Flutter mobile development, you achieve clear modular boundaries, faster build times, and parallel team workflows. Each feature stands alone with its own data, domain, and UI layers. Shared services live in a core module, and routing plus dependency injection are routed through feature-specific initializers. This approach scales gracefully as your app grows, improving maintainability and test coverage.