A dart package that helps to implement basic states for BLoC library to perform, load and fetch data.

Features

• Provides all necessary states for data : init, waiting, value/no value and error states,
• Some helpers performOnState to emit intermediate states while an action is intended to update state : the same state is reemitted with attribute refreshing at true.

Usage

class CounterBehaviorSubject {
  var _value = 0;
  Future<int> _getCounterValueFromRepository() async => _value++;

  Future<void> refresh() => performOnState<int, void>(
      state: () => state,
      emitter: _streamController.add,
      action: (state, emitter) async {
        final result = await _getCounterValueFromRepository();

        if (result == 2) {
          throw 'Error';
        } else if (result > 4) {
          emitter(const NoValueState());
        } else {
          emitter(ValueState(result));
        }
      });

  final BaseState<int> _state = const InitState();
  BaseState<int> get state => _state;

  final _streamController = StreamController<BaseState<int>>();
  late StreamSubscription<BaseState<int>> _streamSubscription;

  Stream<BaseState<int>> get stream =>
      Stream.value(state).followedBy(_streamController.stream);

  Future<void> close() async {
    await _streamSubscription.cancel();
    await _streamController.close();
  }
}

main() async {
  final counterCubit = CounterBehaviorSubject();

  final timer = Timer.periodic(const Duration(milliseconds: 500), (_) async {
    try {
      await counterCubit.refresh();
    } catch (error) {
      // Prevent stop execution for example
    }
  });

  await for (final state in counterCubit.stream) {
    if (state is ReadyState<int>) {
      print('State is refreshing: ${state.refreshing}');

      if (state.hasError) {
        print('Error');
      }

      if (state is WithValueState<int>) {
        print('Value : ${state.value}');
      }

      if (state is NoValueState<int>) {
        timer.cancel();
        print('No value');
      }
    } else {
      print('Waiting for value - $state');
    }
  }
}

The whole code of this example is available in example.

Models

State diagram

Class diagram

Feedback

Please file any issues, bugs or feature requests as an issue on the Github page.