title: Is it possible listen state of many BloC?
body: <p>After asking about state management in Flutter (<a href="https://stackoverflow.com/questions/56886805/difference-between-changenotifierprovider-and-scopedmodel-in-flutter">Difference between ChangeNotifierProvider and ScopedModel in Flutter</a>) without having any answer  I decided to use <a href="https://pub.dev/packages/bloc" rel="nofollow noreferrer">BLoC Package</a> which seems to me the clearest and easiest to use.
  Now in my flutter app i have BlocA, BlocB and BlocC and I want to listen the state changes of BlocA and BlocB from BlocC.</p>
  
  <p>Example with same states/event on all blocs (Updating,Updated/ Update):</p>
  
  <pre><code>class BlocC extends Bloc&lt;CEvent, CState&gt; {
    final BlocA a;
    final BlocB b;
    StreamSubscription aSubscription;
  
    BlocC({@required this.a, @required this.b}) {
      aSubscription = a.state.listen((state) {
        if (state is AUpdated) {
          dispatch(UpdateC());
        }
      });
    }
  
    @override
    CState get initialState =&gt; CUpdating();
  
    @override
    Stream&lt;CState&gt; mapEventToState(CEvent event) async* {
      if (event is UpdateC &amp;&amp; b.currentState is BUpdated) {
        yield* CUpdated();
      }
    }
  ...
  </code></pre>
  
  <p>In this case when dispatching the event from BlocA state the state of BlocB sometimes isn't updated in the _mapEventToState method and my listener not work.
  So I think there is a way to subscribe a bloc to many streams for get the correct state transition of all streams. </p>
  
  <p>Can you help me?</p>