feat(evented_bloc): A new package for Blocs and Cubits with the ability to fire events...

[jovazcode]

Description

The lack of capacity to fire events from Blocs and Cubits makes us having to create and manage what we usually call "temporary states", which is a kind of a "hack" (cause an event is an event, like 'FetchErrorEvent' for example while the state of a Bloc is, at least for me, another usage).

Desired Solution

I usually implement in my projects this kind of Blocs and Cubits. Example:

class CounterCubit extends EventedCubit<int, CounterEvent> {
  CounterCubit() : super(0);

  void increment() {
    emit(state + 1);
    fireEvent(const CounterEvent.incremented()); // <- Here the Cubit fires an "IncrementedEvent"
  }

  void decrement() {
    emit(state - 1);
    fireEvent(const CounterEvent.decremented()); // <- Here the Cubit fires a "DecrementedEvent"
  }
}

My implementation of EventedCubit, is as follow:

/// {@template evented_cubit}
/// Specialized [Bloc] which handles initializing the [Cubit]
/// stream of events.
/// {@endtemplate}
abstract class EventedCubit<State, Event> extends Cubit<State>
    with EventedMixin<Event, State> {
  /// {@macro evented_cubit}
  EventedCubit(super.state) {
    initEvented();
  }
}

I use a mixin on "BlocBase<State>" so that I can put there  all the implementation code (cause I cannot modify your "bloc" stacks!!)

For the app I created a simple Widget which I call "BlocEventListener" (100% similar to your BlocListener):

  @override
  Widget build(BuildContext context) {
    return BlocEventListener<CounterCubit, CounterEvent>(
      listenWhen: (bloc, event) => true,
      listener: (context, cubit, event) {
        /// Handle the event
      },
      child: Row(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          ElevatedButton(
            onPressed: () => context.read<CounterCubit>().increment(),
            child: const Icon(Icons.add),
          ),
          hSpace60,
          ElevatedButton(
            onPressed: () => context.read<CounterCubit>().decrement(),
            child: const Icon(Icons.remove),
          ),
        ],
      ),
    );
  }

Additional Context

What I totally avoid in my apps, is the use of "temporary states" and hacks with "noOps", as shown in the following article:

https://itnext.io/flutter-blocs-at-scale-1-the-state-machine-fce5f086d7b9

[felangel]

Closing this as a duplicate of #4008