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I'm new to coding and AS3. I was reading about adding things to the stage using AS3 and learned about the addChild method. Reading more I found that there are different ways to use it. I also read that some ways are better than others, and that some ways are not good at all and better avoided.

I don't trust those sources though. As a coding newbie I come asking for help, StackOverflow. I'm about to start an addChild heavy project and I want to start it with the right implementations. I trust you, so let me ask you this: What's the correct use of addChild?

I just want to add things to the stage, but I read that it's not good to add them directly to the stage (without further argument though). 

stage.addChild()
this.addChild()
addChild()

Are there other ways? Which one should I use?

Thanks for your time. :)

NPN328
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1 Answers1

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As the top-level container for all display objects in the display list hierarchy, there is only one Stage no matter how many SWF files are loaded into the runtime. So, generally, objects should not be added to the Stage, directly, at all. The only object the Stage should contain is the root object.

Generally, you should not use: stage.addChild()

Adding a DisplayObject to the display list should be performed within the scope of a DisplayObjectContainer.

Each SWF file has an associated ActionScript class, known as the main class of the SWF file which extends a display object. From this class or any child within the hierarchy you may call addChild().

The following are equal, and would add a child within the scope of the current display object container.

this.addChild()
addChild()

The this keyword explicity defines scope; however, is generally implicit when left off.

While a display object added via addChild() is added to the front (top) of all other children, to add a child to a specific index position, use the addChildAt() method.

References:

Jason Sturges
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  • If I use this.addChild() in the global scope, am I adding the element to the stage? – NPN328 Oct 27 '12 at 05:00
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    No, there is [global variable scope](http://help.adobe.com/en_US/ActionScript/3.0_ProgrammingAS3/WS5b3ccc516d4fbf351e63e3d118a9b90204-7f9d.html#WS5b3ccc516d4fbf351e63e3d118a9b90204-7f8c) but no `this` pointer in that context addressing the stage. – Jason Sturges Oct 27 '12 at 05:10
  • There must be more to it, though. Right now I'm trying to `addChild()` to a `ViewStack` and it appears to have no effect. Maybe the SDK? (Flex 3.5) – Opux Sep 03 '15 at 20:57
  • @Opux - Flex 4 introduces Spark architecture, in which you add to the display list using `addVisualElement()`. Flex 3 MX architecture uses `addChild()`; however, there are complexities beyond display list programming. In Flex MXML, components use a `mxmlContent` property for children elements. For example, `ViewStack` doesn't accept just any `DisplayObject`. – Jason Sturges Sep 03 '15 at 21:03