Generic events and additional parameters in Actionscript 3.0?

Question

Assuming the following pattern:

someObjectInstance.addEventListener(MyDisplayObject.EVENT_CONSTANT, _handleMyEvent);


private function _handleMyEvent( event:Eve         


        

Answer 1

If you need custom data to travel with your event, yes, you need to create a custom event class.

Here's a simple example:

package {
    import flash.events.Event;

    public class ColorEvent extends Event {
        public static const CHANGE_COLOR:String = "ChangeColorEvent";

        public var color:uint;

        public function ColorEvent(type:String, color:uint, bubbles:Boolean = false, cancelable:Boolean = false) {
            this.color = color;
            super(type, bubbles, cancelable);
        }

        override public function clone():Event {
            return new ColorEvent(type, color, bubbles, cancelable);
        }
    }
}

Please note that the clone method is NOT optional. You must have this method in your custom class for your event to ever be re-broadcast properly (say when one object gets the event, and then re-dispatches it as it's own).

Now as for dispatching the event, that would work like this (obviously this code would go in a method of class that extends EventDispatcher).

dispatchEvent(new ColorEvent(ColorEvent.CHANGE_COLOR, 0xFF0000));

And finally, to subscribe to the event:

function onChangeColor(event:ColorEvent):void {
    trace(event.color);
}

foo.addEventListener(ColorEvent.CHANGE_COLOR, onChangeColor);