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Flutter Development

Architecture

/lib/features/[feature]
├── /data
│   ├── /datasources      # API, local storage
│   ├── /models           # JSON serialization
│   └── /repositories     # Implementation
├── /domain
│   ├── /entities         # Business objects
│   ├── /repositories     # Interfaces
│   └── /usecases         # Business logic
└── /presentation
    ├── /bloc             # State management
    ├── /pages            # Screens
    └── /widgets          # UI components

BLoC Pattern

// Events
abstract class AuthEvent {}
class LoginRequested extends AuthEvent {
  final String email, password;
  LoginRequested(this.email, this.password);
}

// States
abstract class AuthState {}
class AuthInitial extends AuthState {}
class AuthLoading extends AuthState {}
class AuthSuccess extends AuthState { final User user; }
class AuthFailure extends AuthState { final String error; }

// BLoC
class AuthBloc extends Bloc<AuthEvent, AuthState> {
  AuthBloc(): super(AuthInitial()) {
    on<LoginRequested>(_onLogin);
  }
}

Widgets

• Stateless for pure UI
• Stateful only if local state is needed
• const constructors when possible
• Composition over inheritance

Tests

// Widget test
testWidgets('shows button', (tester) async {
  await tester.pumpWidget(MaterialApp(home: MyWidget()));
  expect(find.byType(ElevatedButton), findsOneWidget);
});

// BLoC test
blocTest<AuthBloc, AuthState>(
  'emits [Loading, Success] on login',
  build: () => AuthBloc(),
  act: (bloc) => bloc.add(LoginRequested('email', 'pass')),
  expect: () => [AuthLoading(), isA<AuthSuccess>()],
);