public static void RegisterListenerCallback(string eventName, UnityAction <UnityAction <int> > listener) { if (Instance.callbackEventDictionary.TryGetValue(eventName, out UnityEvent <UnityAction <int> > thisEvent)) { thisEvent.AddListener(listener); } else { thisEvent = new CallbackEvent(); thisEvent.AddListener(listener); Instance.callbackEventDictionary.Add(eventName, thisEvent); } }