bloc_effects 2.0.0

Cubit and Bloc abstractions and Flutter Widget that make it easy to add UI Effects to the BLoC state management.

SingleLiveEvent pattern implementation for Cubit and Bloc

The abstractions on Cubit and Bloc and Flutter Widget that make it easy to add UI Effects to the BLoC state management using [package:bloc](https://pub.dev/packages/bloc).

Usage

Lets take a look at how to use mixin Effects or class CubitWithEffects to dispatch effects from CounterCubit to a CounterPage and react on them with BlocEffectListener.

ui_effect.dart

abstract class UiEffect {}

class ShowBottomSheet implements UiEffect {
 const ShowBottomSheet({required this.counterValue});
 
 final int counterValue;
}

counter_cubit.dart

class CounterCubit extends Cubit<int> with Effects<UiEffect> {
 CounterCubit() : super(0);

 void increment() => emit(state + 1);

 void onButtonPressed() => emitEffect(ShowBottomSheet(counterValue: state));
}

or the same with the class extension:

class CounterCubit extends CubitWithEffects<int, UiEffect> {
 CounterCubit() : super(0);

 void increment() => emit(state + 1);

 void onButtonPressed() => emitEffect(ShowBottomSheet(counterValue: state));
}

main.dart

void main() => runApp(CounterApp());

class CounterApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: BlocProvider(
        create: (_) => CounterCubit(),
        child: CounterPage(),
      ),
    );
  }
}

counter_page.dart

class CounterPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Counter')),
      body: BlocEffectListener<CounterCubit, UiEffect>(
        listener: (context, effect) {
          if (effect is ShowBottomSheet) {
            showBottomSheet<void>(
              context: context,
              builder: (c) =>
                  Material(
                    child: Container(
                      color: Colors.black12,
                      height: 150,
                    ),
                  ),
            );
          }
        },
        child: const Sizedbox(),
      ),
      floatingActionButton: FloatingActionButton(
        child: const Icon(Icons.upload),
        onPressed: () => context.read<CounterCubit>().onButtonPressed(),
      ),
    );
  }
}

And also BlocWithEffectsObserver can be useful. It extends BlocObserver and add onEffect callback to base observing features:

app_bloc_observer.dart

class AppBlocObserver extends BlocWithEffectsObserver {
 @override
 void onEffect(Object effect) {
   super.onEffect(effect);
   debugPrint('Used effect: $effect');
 }
// Other [BlocObserver] overrides
}