Messenger class for Unity3D

Messenger.cs

/*
 * 
 * Features:
 	* Prevents a MissingReferenceException because of a reference to a destroyed message handler.
 	* Option to log all messages
 	* Extensive error detection, preventing silent bugs
 * 
 * Usage examples:
 	1. Messenger.AddListener<GameObject>("prop collected", PropCollected);
 	   Messenger.Broadcast<GameObject>("prop collected", prop);
 	2. Messenger.AddListener<float>("speed changed", SpeedChanged);
 	   Messenger.Broadcast<float>("speed changed", 0.5f);
 * 
 * Messenger cleans up its evenTable automatically upon loading of a new level.
 * 
 * Don't forget that the messages that should survive the cleanup, should be marked with Messenger.MarkAsPermanent(string)
 * 
 */
 
//#define LOG_ALL_MESSAGES
//#define LOG_ADD_LISTENER
//#define LOG_BROADCAST_MESSAGE
//#define REQUIRE_LISTENER
 
using System;
using System.Collections.Generic;
using UnityEngine;
 
static internal class Messenger {
	#region Internal variables
 
	//Disable the unused variable warning
#pragma warning disable 0414
	//Ensures that the MessengerHelper will be created automatically upon start of the game.
	static private MessengerHelper messengerHelper = ( new GameObject("MessengerHelper") ).AddComponent< MessengerHelper >();
#pragma warning restore 0414
 
	static public Dictionary<string, Delegate> eventTable = new Dictionary<string, Delegate>();
 
	//Message handlers that should never be removed, regardless of calling Cleanup
	static public List< string > permanentMessages = new List< string > ();
	#endregion
	#region Helper methods
	//Marks a certain message as permanent.
	static public void MarkAsPermanent(string eventType) {
#if LOG_ALL_MESSAGES
		Debug.Log("Messenger MarkAsPermanent \t\"" + eventType + "\"");
#endif
 
		permanentMessages.Add( eventType );
	}
 
 
	static public void Cleanup()
	{
#if LOG_ALL_MESSAGES
		Debug.Log("MESSENGER Cleanup. Make sure that none of necessary listeners are removed.");
#endif
 
		List< string > messagesToRemove = new List<string>();
 
		foreach (KeyValuePair<string, Delegate> pair in eventTable) {
			bool wasFound = false;
 
			foreach (string message in permanentMessages) {
				if (pair.Key == message) {
					wasFound = true;
					break;
				}
			}
 
			if (!wasFound)
				messagesToRemove.Add( pair.Key );
		}
 
		foreach (string message in messagesToRemove) {
			eventTable.Remove( message );
		}
	}
 
	static public void PrintEventTable()
	{
		Debug.Log("\t\t\t=== MESSENGER PrintEventTable ===");
 
		foreach (KeyValuePair<string, Delegate> pair in eventTable) {
			Debug.Log("\t\t\t" + pair.Key + "\t\t" + pair.Value);
		}
 
		Debug.Log("\n");
	}
	#endregion
 
	#region Message logging and exception throwing
    static public void OnListenerAdding(string eventType, Delegate listenerBeingAdded) {
#if LOG_ALL_MESSAGES || LOG_ADD_LISTENER
		Debug.Log("MESSENGER OnListenerAdding \t\"" + eventType + "\"\t{" + listenerBeingAdded.Target + " -> " + listenerBeingAdded.Method + "}");
#endif
 
        if (!eventTable.ContainsKey(eventType)) {
            eventTable.Add(eventType, null );
        }
 
        Delegate d = eventTable[eventType];
        if (d != null && d.GetType() != listenerBeingAdded.GetType()) {
            throw new ListenerException(string.Format("Attempting to add listener with inconsistent signature for event type {0}. Current listeners have type {1} and listener being added has type {2}", eventType, d.GetType().Name, listenerBeingAdded.GetType().Name));
        }
    }
 
    static public void OnListenerRemoving(string eventType, Delegate listenerBeingRemoved) {
#if LOG_ALL_MESSAGES
		Debug.Log("MESSENGER OnListenerRemoving \t\"" + eventType + "\"\t{" + listenerBeingRemoved.Target + " -> " + listenerBeingRemoved.Method + "}");
#endif
 
        if (eventTable.ContainsKey(eventType)) {
            Delegate d = eventTable[eventType];
 
            if (d == null) {
                throw new ListenerException(string.Format("Attempting to remove listener with for event type \"{0}\" but current listener is null.", eventType));
            } else if (d.GetType() != listenerBeingRemoved.GetType()) {
                throw new ListenerException(string.Format("Attempting to remove listener with inconsistent signature for event type {0}. Current listeners have type {1} and listener being removed has type {2}", eventType, d.GetType().Name, listenerBeingRemoved.GetType().Name));
            }
        } else {
            throw new ListenerException(string.Format("Attempting to remove listener for type \"{0}\" but Messenger doesn't know about this event type.", eventType));
        }
    }
 
    static public void OnListenerRemoved(string eventType) {
        if (eventTable[eventType] == null) {
            eventTable.Remove(eventType);
        }
    }
 
    static public void OnBroadcasting(string eventType) {
#if REQUIRE_LISTENER
        if (!eventTable.ContainsKey(eventType)) {
            throw new BroadcastException(string.Format("Broadcasting message \"{0}\" but no listener found. Try marking the message with Messenger.MarkAsPermanent.", eventType));
        }
#endif
    }
 
    static public BroadcastException CreateBroadcastSignatureException(string eventType) {
        return new BroadcastException(string.Format("Broadcasting message \"{0}\" but listeners have a different signature than the broadcaster.", eventType));
    }
 
    public class BroadcastException : Exception {
        public BroadcastException(string msg)
            : base(msg) {
        }
    }
 
    public class ListenerException : Exception {
        public ListenerException(string msg)
            : base(msg) {
        }
    }
	#endregion
 
	#region AddListener
	//No parameters
    static public void AddListener(string eventType, Callback handler) {
        OnListenerAdding(eventType, handler);
        eventTable[eventType] = (Callback)eventTable[eventType] + handler;
    }
 
	//Single parameter
	static public void AddListener<T>(string eventType, Callback<T> handler) {
        OnListenerAdding(eventType, handler);
        eventTable[eventType] = (Callback<T>)eventTable[eventType] + handler;
    }
 
	//Two parameters
	static public void AddListener<T, U>(string eventType, Callback<T, U> handler) {
        OnListenerAdding(eventType, handler);
        eventTable[eventType] = (Callback<T, U>)eventTable[eventType] + handler;
    }
 
	//Three parameters
	static public void AddListener<T, U, V>(string eventType, Callback<T, U, V> handler) {
        OnListenerAdding(eventType, handler);
        eventTable[eventType] = (Callback<T, U, V>)eventTable[eventType] + handler;
    }
	#endregion
 
	#region RemoveListener
	//No parameters
    static public void RemoveListener(string eventType, Callback handler) {
        OnListenerRemoving(eventType, handler);   
        eventTable[eventType] = (Callback)eventTable[eventType] - handler;
        OnListenerRemoved(eventType);
    }
 
	//Single parameter
	static public void RemoveListener<T>(string eventType, Callback<T> handler) {
        OnListenerRemoving(eventType, handler);
        eventTable[eventType] = (Callback<T>)eventTable[eventType] - handler;
        OnListenerRemoved(eventType);
    }
 
	//Two parameters
	static public void RemoveListener<T, U>(string eventType, Callback<T, U> handler) {
        OnListenerRemoving(eventType, handler);
        eventTable[eventType] = (Callback<T, U>)eventTable[eventType] - handler;
        OnListenerRemoved(eventType);
    }
 
	//Three parameters
	static public void RemoveListener<T, U, V>(string eventType, Callback<T, U, V> handler) {
        OnListenerRemoving(eventType, handler);
        eventTable[eventType] = (Callback<T, U, V>)eventTable[eventType] - handler;
        OnListenerRemoved(eventType);
    }
	#endregion
 
	#region Broadcast
	//No parameters
    static public void Broadcast(string eventType) {
#if LOG_ALL_MESSAGES || LOG_BROADCAST_MESSAGE
		Debug.Log("MESSENGER\t" + System.DateTime.Now.ToString("hh:mm:ss.fff") + "\t\t\tInvoking \t\"" + eventType + "\"");
#endif
        OnBroadcasting(eventType);
 
        Delegate d;
        if (eventTable.TryGetValue(eventType, out d)) {
            Callback callback = d as Callback;
 
            if (callback != null) {
                callback();
            } else {
                throw CreateBroadcastSignatureException(eventType);
            }
        }
    }
 
	//Single parameter
    static public void Broadcast<T>(string eventType, T arg1) {
#if LOG_ALL_MESSAGES || LOG_BROADCAST_MESSAGE
		Debug.Log("MESSENGER\t" + System.DateTime.Now.ToString("hh:mm:ss.fff") + "\t\t\tInvoking \t\"" + eventType + "\"");
#endif
        OnBroadcasting(eventType);
 
        Delegate d;
        if (eventTable.TryGetValue(eventType, out d)) {
            Callback<T> callback = d as Callback<T>;
 
            if (callback != null) {
                callback(arg1);
            } else {
                throw CreateBroadcastSignatureException(eventType);
            }
        }
	}
 
	//Two parameters
    static public void Broadcast<T, U>(string eventType, T arg1, U arg2) {
#if LOG_ALL_MESSAGES || LOG_BROADCAST_MESSAGE
		Debug.Log("MESSENGER\t" + System.DateTime.Now.ToString("hh:mm:ss.fff") + "\t\t\tInvoking \t\"" + eventType + "\"");
#endif
        OnBroadcasting(eventType);
 
        Delegate d;
        if (eventTable.TryGetValue(eventType, out d)) {
            Callback<T, U> callback = d as Callback<T, U>;
 
            if (callback != null) {
                callback(arg1, arg2);
            } else {
                throw CreateBroadcastSignatureException(eventType);
            }
        }
    }
 
	//Three parameters
    static public void Broadcast<T, U, V>(string eventType, T arg1, U arg2, V arg3) {
#if LOG_ALL_MESSAGES || LOG_BROADCAST_MESSAGE
		Debug.Log("MESSENGER\t" + System.DateTime.Now.ToString("hh:mm:ss.fff") + "\t\t\tInvoking \t\"" + eventType + "\"");
#endif
        OnBroadcasting(eventType);
 
        Delegate d;
        if (eventTable.TryGetValue(eventType, out d)) {
            Callback<T, U, V> callback = d as Callback<T, U, V>;
 
            if (callback != null) {
                callback(arg1, arg2, arg3);
            } else {
                throw CreateBroadcastSignatureException(eventType);
            }
        }
    }
	#endregion
}
 
//This manager will ensure that the messenger's eventTable will be cleaned up upon loading of a new level.
public sealed class MessengerHelper : MonoBehaviour {
	void Awake ()
	{
		DontDestroyOnLoad(gameObject);	
	}
 
	//Clean up eventTable every time a new level loads.
	public void OnDisable() {
		Messenger.Cleanup();
	}
}

public delegate void Callback();
public delegate void Callback<T>(T arg1);
public delegate void Callback<T, U>(T arg1, U arg2);
public delegate void Callback<T, U, V>(T arg1, U arg2, V arg3);