Passing parameters to event listeners / handlers

Question

How do you pass parameters / variables through event listeners? I\'ve overcome this problem fairly effectively using anonymous functions; which is an incredibly simple solut

Answer 1

It is probably better practice to make a custom class that extends MovieClip for your thumnbnail, and have that thumbnail dispatch a custom Event class that has a place to store your data:

Make a custom URLEvent that can store the url property along with the event

package{

import flash.events.Event;

public class URLEvent extends Event{

    public var url:String;
    public static const CLICK:String = "URLEventClick"

    public function URLEvent(type:String, url:String = "", bubbles:Boolean = false, cancelable:Boolean=false){
        super(type, bubbles, cancelable);
        this.url = url;
    }

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

Make a custom thumbnail class that can store the url variable, and sends a URLEvent when clicked:

package{

import flash.display.MovieClip;
import flash.events.MouseEvent;

public class Thumbnail extends MovieClip{

    protected var url:String;

    public function Thumbnail(url:String){
        this.url = url;
        addEventListener(MouseEvent.CLICK,clickHandler);
    }

    //the thumbnail captures its own click and dispatches a custom event
    protected function clickHandler(event:MouseEvent):void{
        dispatchEvent(new URLEvent(URLEvent.CLICK,url));
    }

}

Now you can use your Thumbnail class to load each image:

tempThumb.addEventListener(URLEvent.CLICK,tempThumbClickHandler);

function tempThumbClickHandler(event:URLEvent):void{
//we can get the url property direct from the URLEvent
    loadImage(event.url);
}

This method is much better OOP practice, as you do not need to know what type of object your event.target is - you know from the event type exactly what type of data will be sent with each event.