design-patternslisted

# Flutter Design Patterns Skill Quick reference for common design patterns in Flutter with Dart 3.11, Riverpod 3.x, and Clean Architecture. ## When to Use - User asks to implement a specific pattern - Designing reusable or extensible features - Refactoring rigid, duplicated, or untestable code ## Quick Reference: When to Use What | Problem | Pattern | Use When | |---------|---------|----------| | Flexible UI with variations | **Widget Composition** | Building reusable component APIs | | Data layer abstraction | **Repository** | API calls, local DB, caching strategy | | Screen business logic | **MVVM (AsyncNotifier)** | Feature screens with async data | | Swappable algorithms | **Strategy** | Payment processing, sorting, auth methods | | Reactive data streams | **Observer (Streams)** | Real-time updates, WebSocket, SSE | | Exhaustive state handling | **Sealed Class Union** | Loading/success/error, navigation events | | Expensive shared resource | **Singleton (Riverpod)** | Dio client, SharedPreferences, analytics | | Platform-specific widgets | **Factory** | iOS vs Android adaptive UI | --- ## Widget Composition ### Slot Pattern **Problem:** Build flexible widgets that accept custom content in specific positions. ```dart /// Reusable list tile with configurable slots class AppListTile extends StatelessWidget { const AppListTile({ required this.title, this.subtitle, this.leading, this.trailing, this.onTap, super.key, }); final Widget titl