Signals

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Robert Penner shows to the world his new Event System called Signals it’s a cool way for managing Events in AS3 inspired by C# events and signals/slots in Qt.

Concept

  • A Signal is essentially a mini-dispatcher specific to one event, with its own array of listeners.
  • A Signal gives an event a concrete membership in a class.
  • Listeners subscribe to real objects, not to string-based channels.
  • Event string constants are no longer needed.

Features

  • Remove all event listeners:
  • Retrieve the number of listeners
  • Listeners can be added for a one-time call and removed automatically on dispatch:
  • Any object type can be dispatched to listeners. But using IEvent will enable full functionality.
  • A Signal can be initialized with an event class that will validate event objects on dispatch (optional):
  • If the Signal’s event class is specified, each listener is checked on add() to ensure it declares at least one argument.
  • 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).
  • Code was developed test-first.

Sintax

comparison:

// with EventDispatcher
button.addEventListener(MouseEvent.CLICK, onClick);

// Signal equivalent; past tense is recommended
button.clicked.add(onClicked);

Create a Signal for a class:

////// in Item class:
// Recommended: make the signal read-only.
protected var _ready:Signal;
public function get ready():Signal { return _ready; }

public function Item()
{
    _ready = new Signal(this, ReadyEvent);
}

protected function sendReady():void
{
    _ready.dispatch(new ReadyEvent());
}

////// in another class:
var item:Item = new Item();
protected function onItemReady(e:ReadyEvent):void { ... }

item.ready.add(onItemReady);

more info on Signals

AS3 Signals Getting Stronger

The Community Responds to AS3 Signals

My New AS3 Event System: Signals

more info on AS3 Events

My Critique of AS3 Events – Part 1

AS3 Events – 7 things I’ve learned from community

My Critique of AS3 Events – Part 2

i like this kind of people, never comfortable, always trying to make improvements, changing the way we see things and Robert Penner is not and exception.

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