5 دیزاین پترن مهم برای همه مهندسین فلاتر

class SettingsManager {
  static final SettingsManager _instance = SettingsManager._internal();

  factory SettingsManager() => _instance;

  SettingsManager._internal();

  ThemeData _themeData = ThemeData.light();

  void switchTheme() {
    _themeData = _themeData.brightness == Brightness.light ? ThemeData.dark() : ThemeData.light();
    // Notify listeners of theme change (implementation omitted for brevity)
  }

  ThemeData getTheme() => _themeData;
}

abstract class ButtonFactory {
  Widget createButton(String text);
}

class PrimaryButtonFactory implements ButtonFactory {
  @override
  Widget createButton(String text) => ElevatedButton(onPressed: null, child: Text(text));
}

class SecondaryButtonFactory implements ButtonFactory {
  @override
  Widget createButton(String text) => TextButton(onPressed: null, child: Text(text));
}

// Usage
ButtonFactory buttonFactory = (isPrimary) => isPrimary ? PrimaryButtonFactory() : SecondaryButtonFactory();
Widget myButton = buttonFactory(true).createButton("Click Me"); // Creates a primary button

class RoundedButton extends StatelessWidget {
  final String text;
  final VoidCallback onPressed;


  const RoundedButton({required this.text, required this.onPressed});


  @override
  Widget build(BuildContext context) {
    return TextButton(
      onPressed: onPressed,
      child: Container(
        padding: EdgeInsets.all(16.0),
        decoration: BoxDecoration(
          color: Colors.blue,
          borderRadius: BorderRadius.circular(10.0),
        ),
        child: Text(text, style: TextStyle(color: Colors.white)),
      ),
    );
  }
}


// Usage
Widget myScreen = Scaffold(
  body: Center(
    child: RoundedButton(text: 'Click Me', onPressed: () => print('Button Pressed')),
  ),
);

@immutable
abstract class CounterEvent {}


// Events
class IncrementEvent extends CounterEvent {}


class DecrementEvent extends CounterEvent {}


// State
class CounterState {
  final int counter;


  CounterState(this.counter);
}


// Bloc
class CounterBloc extends Bloc {
  CounterBloc() : super(CounterState(0));


  @override
  Stream mapEventToState(CounterEvent event) async* {
    if (event is IncrementEvent) {
      yield CounterState(state.counter + 1);
    } else if (event is DecrementEvent) {
      yield CounterState(state.counter - 1);
    }
  }
}


// Usage (in UI)
Widget build(BuildContext context) {
  return BlocProvider(
    create: (context) => CounterBloc(),
    child: Scaffold(
      appBar: AppBar(title: Text('Counter')),
      body: Column(
        mainAxisAlignment: MainCenter,
        children: [
          BlocBuilder(
            builder: (context, state) => Text('Count: ${state.counter}'),
          ),
          Row(
            mainAxisAlignment: MainSpaceEvenly,
            children: [
              ElevatedButton(
                onPressed: () => BlocProvider.of(context).add(IncrementEvent()),
                child: Icon(Icons.add),
              ),
              ElevatedButton(
                onPressed: () => BlocProvider.of(context).add(DecrementEvent()),
                child: Icon(Icons.remove),
              ),
            ],
          ),
        ],
      ),
    ),
  );
}