In Flutter Redux Epic middleware, how i can dispatch a action after the stream variable changes?

Question

In Flutter Redux Epic middleware, how i can dispatch a action after stream variable changes?

A simple example of the EpicMiddleware:

final allEpics = combineEpics<AppState>([hourglassesStream]);

Firestore firestore = Firestore.instance;


Stream<dynamic> hourglassesStream(
    Stream<dynamic> actions, EpicStore<AppState> store) {
  return Observable(actions)
      .ofType(TypeToken<ConnectToDataSourceAction>())
      .switchMap((ConnectToDataSourceAction requestAction) {
    getHourglasses(action.userId).listen((hourglass) {

      LoadHourglassesHistoryAction(
          hourglass.map(Hourglass.fromEntity).toList());
    });
  });
}

Observable<List<HourglassEntity>> getHourglasses(String userId) {
  return Observable(firestore
      .collection('users')
      .document(userId)
      .collection('hourglassLogs')
      .snapshots()
      .map((snapshot) {
    return snapshot.documents.map((doc) {
      return HourglassEntity(
        doc['completedTime'],
        doc['projectName'],
        doc['userId'],
      );
    }).toList();
  }));
}

I tried some diferents methods to dispatch this LoadHourglassesHistoryAction after the hourglass variable changed from observable, but dont dispatch. Is possible dispatch a action after the Observable change?

Used packages:
redux_epics: ^0.10.0 & rxdart: ^0.18.0

Answer 1

You have to return the observable/stream, to dispatch the action

Stream<dynamic> hourglassesStream(
    Stream<dynamic> actions, EpicStore<AppState> store) {
  return Observable(actions)
      .ofType(TypeToken<ConnectToDataSourceAction>())
      .switchMap((ConnectToDataSourceAction requestAction) {
    return getHourglasses(action.id).map((hourglass) =>
     LoadHourglassesHistoryAction(
          hourglass.map(Hourglass.fromEntity).toList())
    );
  });
}