Actionscript 3.0 prototyping, viable but costly

Back in the Flash 6 – Flash 8 world, I was a big fan of prototyping, mostly because of the limitations of MovieClip inheritance. I haven’t needed to use it at all in Actionscript 3 but I was still curious about how to accomplish it nowadays. Here’s the example I was able to create in Flex.

Sprite.prototype.spriteHelper = new SpriteHelper();
Sprite.prototype.rotateTo = function(deg:int):void{
	var sh:SpriteHelper = this["spriteHelper"]; = this;
	import flash.display.Sprite;
	import flash.utils.Timer;

	public class SpriteHelper
		public var _degreeTo:int = 0;
		public var _degCount:int = 0;
		public var _degTimer:Timer = null;
		public var target:Sprite;
		public function rotateTo(deg:int):void{
			_degreeTo = deg;
			_degCount = 0;
			_degTimer = new Timer(10);
			_degTimer.addEventListener(TimerEvent.TIMER, doAnimateRotation);
		public function doAnimateRotation(event:TimerEvent):void{
			if(_degCount <= 40){
				target.rotation = _degreeTo * (_degCount/40);
				_degTimer.removeEventListener(TimerEvent.TIMER, doAnimateRotation);
				_degTimer = null;
<mx:Box id="myContainer" backgroundColor="#FF0000" width="100" height="100" right="40" y="0" creationComplete="myContainer['rotateTo'](50)"/>

You’ll notice 2 things in the implementation here. Since Sprite is a statically defined class, accessing the prototype chain requires bracket syntax ala myContainer[‘rotateTo’](50), and secondly, most of the functionality of rotateTo has been moved into a separate class. The reason for the latter point is because accessing the prototype chain is costly, as it has to recurse through the inheritance chain until it finds the class with the property. As a result I’ve limited the prototype lookups to just spriteHelper and I move all the functionality into there.

Another thing I found in the docs is that every class creates a prototype chain by default, so merely adding prototype definitions has no effect on the creation of that object.

RegExp pattern for creating file safe names

Different operating systems restrict specific characters from being used in file and folder names. The following code snippet will allow you to trim those special characters when creating File references in AIR.

var fileSafePattern:RegExp = new RegExp('["\\\\ *?<>|:]', 'gi');
var fileSafeName:String = myString.replace(fileSafePattern, "_");
var myFile:File = File.applicationStorageDirectory.resolvePath(fileSafeName);

eBay Desktop demo

I’ve been doing a few presentations on Apollo the past few months centered around accessing eBays web services. While the app shown has remained just a “prototype”, I’m finally able to talk openly about the product and the fact that we’re moving into an official eBay application with a beta program coming soon.

The beta signup is public now so if your interested in getting involved early on and getting your feedback heard, you can sign up over at . I’m planning on watching the results of the beta very closely and trying to interact with a lot of users to get their opinions. We’ve got an amazing opportunity to rebuild eBays interface from the ground up and want to make sure every aspect of using eBay gets improved in the process. So feel free to send me your thoughts through this blog or on the beta site.

If you want to see a demo of the application, I gave a presentation recorded at Adobes ApolloCamp back in March.

Hacking away at UI development