Optimized Signal to not clone the listeners array on dispatch().

src/org/osflash/signals/Signal.as

@@ -18,6 +18,7 @@ package org.osflash.signals
 		protected var _valueClasses:Array;		// of Class
 		protected var listeners:Array;			// of Function
 		protected var onceListeners:Dictionary;	// of Function
+		protected var dispatching:Boolean = false;;
 
 		/**
 		 * Creates a Signal instance to dispatch value objects.
@@ -73,14 +74,15 @@ package org.osflash.signals
 		{
 			var index:int = listeners.indexOf(listener);
 			if (index == -1) return;
+			if (dispatching) listeners = listeners.slice();
 			listeners.splice(index, 1);
 			delete onceListeners[listener];
 		}
 
 		/** @inheritDoc */
 		public function removeAll():void
 		{
-			listeners.length = 0;
+			listeners = [];
 			onceListeners = new Dictionary();
 		}
 
@@ -104,35 +106,37 @@ package org.osflash.signals
 
 			if (!listeners.length) return;
 
+			dispatching = true;
+
 			//TODO: investigate performance of various approaches
 			//// Call listeners.
 			var listener:Function;
 			switch (valueObjects.length)
 			{
 				case 0:
-					// Clone listeners array because add/remove may occur during the dispatch.
-					for each (listener in listeners.slice())
+					for each (listener in listeners)
 					{
 						if (onceListeners[listener]) remove(listener);
 						listener();
 					}
 					break;
 
 				case 1:
-					for each (listener in listeners.slice())
+					for each (listener in listeners)
 					{
 						if (onceListeners[listener]) remove(listener);
 						listener(valueObjects[0]);
 					}
 					break;
 
 				default:
-					for each (listener in listeners.slice())
+					for each (listener in listeners)
 					{
 						if (onceListeners[listener]) remove(listener);
 						listener.apply(null, valueObjects);
 					}
 			}
+			dispatching = false;
 		}
 
 		protected function setValueClasses(valueClasses:Array):void
@@ -165,6 +169,8 @@ package org.osflash.signals
 				return;
 			}
 
+			if (dispatching) listeners = listeners.slice();
+
 			// Don't add the same listener twice.
 			if (listeners.indexOf(listener) >= 0)
 				return;

tests/org/osflash/signals/SignalTest.as

@@ -166,9 +166,10 @@ package org.osflash.signals
 		}
 		//////
 		[Test]
-		public function add_2_listeners_first_listener_removes_itself_should_call_2nd_listener():void
+		public function dispatch_2_listeners_1st_listener_removes_itself_then_2nd_listener_is_still_called():void
 		{
 			completed.add(selfRemover);
+			// addAsync verifies the second listener is called
 			completed.add(addAsync(newEmptyHandler(), 10));
 			completed.dispatch();
 		}
@@ -177,6 +178,18 @@ package org.osflash.signals
 		{
 			completed.remove(selfRemover);
 		}
+		//////
+		[Test]
+		public function dispatch_2_listeners_1st_listener_removes_all_then_2nd_listener_is_still_called():void
+		{
+			completed.add(addAsync(allRemover, 10));
+			completed.add(addAsync(newEmptyHandler(), 10));
+			completed.dispatch();
+		}
 
+		private function allRemover():void
+		{
+			completed.removeAll();
+		}
 	}
 }