Ubacoda.com is an independant developer of mobile applications. Welcome to the ubacoda.com blog!

The Scope of Things

Wed Oct 14 02:20:48 2009

Sometimes it can be a little difficult to get the specific "child" you want in ActionScript 3 by calling its name directly. Also, the use of getChildAt() and getChildByName("") doesn't work because they are outside the scope of the current class in question. Well, this is where you could try casting.

For example, say that I have three classes. One called Main.as, one called Second.as and one called Third.as, each containing a single MovieClip containing a Square, Circle and Triangle respectively. Main imports Second and and Third and so becomes their "parent". The result is a Square, Circle and Triangle on the stage.

Now say that I want to access Third from Second to change the scale or some other property of Third's triangle. Well, I would need to use the this.parent.getChildAt(position).getChildAt(position) or maybe this.parent.getChildByName("second).getChildByName("triangle"), that is, if I had given them names. However, this is where you would run into problems. Flex/Flash just doesn't know what you are talking about. Instead, by casting all instances and clips to "MovieClip" and holding them inside variables, you will ensure that Flex/Flash knows exactly what you want to access and what type of object it is.

Here's what I'm talking about

    //this.parent.getChildAt(1).getChildAt(0) just doesn't work. It's outside the scope
    //of the class called Third.

    var sec:MovieClip = MovieClip(this.parent.getChildAt(1));
    var tri:MovieClip = MovieClip(sec.getChildAt(0));
    tri.scaleX = 2;

I know that some will complain that there is a better way to code and a good coder wouldn't code this way, and I would say I agree for the most part. However sometimes, whether it be a quick fix, or a quick add-on to an existing application coded by someone else, sometimes this will come in handy. After all, we can't guarantee the work of others.

If you would like a closer look, I have provided some fully annotated files here

FXG in ActionScript 3

Mon Oct 12 12:58:53 2009

With the introduction of the Flex 4 SDK (Gumbo), it is now possible to import FXG files into your ActionScript and MXML projects. In this example, I will be using an illustration of a flower, aptly named Flower.fxg which was created in and exported from Illustrator CS4.

I would also like to add that what I'm about to do is also possible using SVG files, and for anyone using TextMate or FlashDevelop, this looks a very promising replacement to the Flash IDE and library.

First, you need to create a package and embed your vector graphic as a Class. Embedding required the Flex SDK, so for Flash users who wish to try this out, you will need to get the Flex SDK and point flash in the right direction.

The finished article looks something like this:

package  {
      import flash.display.Sprite;
      import flash.events.MouseEvent;

      [SWF(width='500', height='500', backgroundColor='#FFFFFF', frameRate='60')]
	
      public class Main extends Sprite {
 	
	    [Embed(source='Flower.fxg')]
	    private var Flower:Class;
	    private var flower:Sprite = new Flower();
 
	    public function Main() {
	       addChild(flower).addEventListener(MouseEvent.CLICK, clickHandler);
	       flower.buttonMode = true;
	    }
		
	    private function clickHandler(event:MouseEvent):void {
	       trace("Flower Clicked");
            }
      }
}

After this class has been created, simply compile it making sure that the FXG file is where it's supposed to be. In my case, I used TextMate and the FLEX 4 SDK to compile. The result is as follows.