dart-flutter-patterns

Riverpod state management uses @riverpod annotated providers for async data and Notifier classes for complex mutations. Derived providers can watch other providers to compute values like cart totals, and auto-dispose keeps memory usage bounded.

BLoC/Cubit suits event-driven flows with explicit state transitions and blocTest support, while Riverpod offers compile-safe dependency injection and derived providers. Provider is the simplest option for basic dependency injection and change notification.

GoRouter auth guards use the redirect callback combined with refreshListenable wired to your auth state stream. The redirect checks authentication status and returns '/login' for unauthenticated users, re-evaluating automatically when auth state changes.

Using BuildContext after an await crashes when the widget was unmounted during the async gap. Always check the mounted property before calling context-dependent methods like navigation or ScaffoldMessenger in StatefulWidget async handlers.

Dio supports token refresh through an InterceptorsWrapper onError handler that detects 401 responses, attempts a refresh, and retries the original request. A one-time retry flag in requestOptions.extra prevents infinite retry loops.

Avoid late when initialization timing is uncertain, since it defers null errors to runtime. It is acceptable only when initialization is guaranteed before first access, such as AnimationController setup in initState; otherwise prefer nullable fields with explicit checks.