eventhub.dart

class Store {
  Store([Store parent = null]) {
      this.emit = parent == null ? (dynamic action) {
        if (_subscribers.containsKey(action)) {
          _subscribers[action].forEach((cb) => cb());
        }
      } : parent.emit;
  }
  Map<Action, Set<Function>> _subscribers = new Map();
	Function subscribe(List<Action> actions, Function callback) {
    actions.forEach((action) {
    	_subscribers.putIfAbsent(action, () => new Set());
    	_subscribers[action].add(callback);  
    });

    
    return () {
      actions.forEach((action) {
    	  _subscribers[action].remove(callback);   
      });
    };
  }
  void Function(dynamic action) emit;
}

enum Action {
  ChangeCount,
  ChangeFoo
}

class OtherStore extends Store {
  OtherStore(Store parent) : super(parent);
  
  String foo = "bar";
  
  void changeFoo() {
    foo += "!!!";
    emit(Action.ChangeFoo);
  }
}

class MyStore extends Store {
  OtherStore other;
  
  MyStore() {
    this.other = new OtherStore(this);
  }
  
  int count = 0;
  
  void changeCount() {
    ++count;
    emit(Action.ChangeCount);
  }
}

void main() {
	final store = MyStore();
 
  store.subscribe([Action.ChangeCount, Action.ChangeFoo], () {
    print("hey!");
  });
    
  
  store.changeCount();
  store.other.changeFoo();
}