And an excellent question that is. The MovieClip class changed somewhat significantly between ActionScript 2.0 and ActionScript 3.0. Now, in ActionScript 3.0 you use the “new MovieClip()” constructor to create a new movie clip (which is a lot more consistent with the rest of the Flash Player API, ie: new Sprite(), new MovieClip(), new Array(), new Date(), new Video(), etc).

As for depth, there are several methods for handling depth. In no particular order:

addChildAt(child:DisplayObject, index:int):DisplayObject
getChildAt(index:int):DisplayObject
getChildIndex(child:DisplayObject):int
removeChildAt(index:int):DisplayObject
setChildIndex(child:DisplayObject, index:int):void
swapChildren(child1:DisplayObject, child2:DisplayObject):void
swapChildrenAt(index1:int, index2:int):void

(Taken from the MovieClip class in the Flash CS3 LiveDocs.)

So, the general idea is that the “DisplayObject” in question is your MovieClip symbol, and the “index” is the current depth (or desired depth, depending on the method).

Here’s a pretty crude example of a few of the methods (I tested this in the main timeline of Flash CS3, since I already had it open, you may need to tweak somewhat if you’re using Flex):

var box1:MovieClip = new MovieClip();
box1.graphics.beginFill(0xFF0000, 0.1);
box1.graphics.drawRect(0, 0, 100, 100);
box1.graphics.endFill();
box1.x = 10;
box1.y = 10;
addChild(box1);

var box2:MovieClip = new MovieClip();
box2.graphics.beginFill(0x00FF00, 0.2);
box2.graphics.drawRect(0, 0, 100, 100);
box2.graphics.endFill();
box2.x = 30;
box2.y = 40;
addChildAt(box2, 0);

var label1:TextField = new TextField();
label1.autoSize = TextFieldAutoSize.LEFT;
label1.text = String(getChildIndex(box1));
box1.addChild(label1);

var label2:TextField = new TextField();
label2.autoSize = TextFieldAutoSize.LEFT;
label2.text = String(getChildIndex(box2));
box2.addChild(label2);

For more information, you can read the “Display programming” chapter of Programming ActionScript 3.0.

Hope that helps,
Peter

dormouse