Features

Signals have many features not available from Flash’s EventDispatcher.

• Remove all event listeners:
  

  signal.removeAll();
  

• Retrieve the number of listeners:
  

  trace( signal.numListeners );
  

• Listeners can be added for a one-time call and removed automatically on dispatch:
  

  signal.addOnce(theListener); // result: signal has one listener
  signal.dispatch(theEvent);   // result: theListener is called, signal now has no listeners
  

• Any object type can be dispatched to listeners; no flash.events.Event restriction.
• You can dispatch your value objects themselves and avoid creating so many Event subclasses.
• Any number of arguments can be dispatched to listeners, from zero to many.
• A Signal can be initialized with value classes that will validate value objects on dispatch (optional):
  

  // A Signal that will dispatch a String and an integer:
  progress = new Signal(String, int);
  //later:
  progress.dispatch(); // will throw ArgumentError 
  progress.dispatch('The Answer'); // will throw ArgumentError 
  progress.dispatch('The Answer', 42.5); // will throw ArgumentError 
  progress.dispatch('The Answer', 42); // will succeed
  

• If the Signal has any value classes specified, each listener is checked on `add()` to ensure it declares enough arguments for the value objects.
• Signals can be placed in interfaces to indicate the events dispatched by a class.
• Events can bubble recursively through `.parent` independent of the display list (experimental).