flutter-development

Flutter Development Patterns

Modern Flutter patterns for cross-platform mobile, web, and desktop development.

CRITICAL: Agentic-First Flutter Development

Pre-Development Verification (MANDATORY)

Before writing ANY Flutter code:

1. CHECK FLUTTER INSTALLATION
   → run_terminal_cmd("flutter --version")
   → run_terminal_cmd("flutter doctor")
   
2. VERIFY CURRENT VERSIONS (use web_search)
   → web_search("Flutter stable version December 2024")
   → web_search("Dart SDK version December 2024")
   
3. CHECK EXISTING PROJECT
   → Does pubspec.yaml exist? Read it first!
   → What Flutter/Dart SDK is specified?
   → Are dependencies already installed?
   
4. FOR NEW PROJECTS - USE flutter create
   → NEVER manually create pubspec.yaml from scratch
   → run_terminal_cmd("flutter create my_app")

CLI-First Flutter Development

ALWAYS use Flutter CLI:

# Project creation (NEVER manually create pubspec.yaml)
flutter create my_app
flutter create --org com.example my_app
flutter create --template package my_package

# Add dependencies (NEVER manually edit pubspec.yaml for adding)
flutter pub add provider
flutter pub add go_router
flutter pub add flutter_bloc
flutter pub add dio
flutter pub add freezed --dev
flutter pub add build_runner --dev

# Get dependencies (ALWAYS after any pubspec change)
flutter pub get

# Code generation (for freezed, json_serializable)
dart run build_runner build --delete-conflicting-outputs

# Verify project health
flutter analyze
flutter test

Post-Edit Verification

After ANY Flutter code changes, ALWAYS run:

# Get dependencies
flutter pub get

# Analyze for issues
flutter analyze

# Run tests
flutter test

# Check formatting
dart format --set-exit-if-changed .

Common Dart/Flutter Syntax Traps (Avoid These!)

// WRONG: Missing const for immutable widgets
Widget build(BuildContext context) {
  return Container(  // Should be const Container()
    child: Text('Hello'),
  );
}

// CORRECT: Use const where possible
Widget build(BuildContext context) {
  return const Container(
    child: Text('Hello'),
  );
}

// WRONG: Not disposing controllers
class _MyWidgetState extends State<MyWidget> {
  final controller = TextEditingController();
  // Missing dispose!
}

// CORRECT: Always dispose controllers
class _MyWidgetState extends State<MyWidget> {
  final controller = TextEditingController();
  
  @override
  void dispose() {
    controller.dispose();
    super.dispose();
  }
}

// WRONG: Using setState after dispose
void _onDataLoaded(data) async {
  await fetchMore();
  setState(() {  // Might be called after dispose!
    this.data = data;
  });
}

// CORRECT: Check mounted before setState
void _onDataLoaded(data) async {
  await fetchMore();
  if (mounted) {
    setState(() {
      this.data = data;
    });
  }
}

// WRONG: Missing required in named parameters (Dart 3+)
void greet({String name}) { }  // Error in null-safe Dart

// CORRECT: Use required for non-nullable required params
void greet({required String name}) { }