flutter-apply-architecture-best-practices

Divide the app into UI, Data, and optional Domain layers. Use MVVM in the UI layer with ChangeNotifier ViewModels, Repositories as the single source of truth in the Data layer, and Use Case classes only when business logic is complex or shared across ViewModels.

Use a hybrid approach: group UI components by feature under lib/ui/features, and group Data and Domain code by type under lib/data (models, repositories, services) and lib/domain (models, use_cases). Shared widgets and themes go in lib/ui/core.

Add Use Case classes only when business logic clutters the ViewModel or must be reused across multiple ViewModels. For simple CRUD features, skip the domain layer and let ViewModels call Repositories directly.

Extend ChangeNotifier in the ViewModel and expose immutable state getters. In the View, wrap widgets in ListenableBuilder or AnimatedBuilder to rebuild when the ViewModel calls notifyListeners, keeping the View free of business logic.

Services are stateless wrappers around external APIs like HTTP clients or local databases, returning raw API models. Repositories consume one or more Services, transform raw models into domain models, and handle caching, offline sync, and retry logic.