how to get id of BorderContainer at runtime in Flex - actionscript-3

Question

I am getting error while attempting to get id of BorderContainer at runtime. I tried using getStyle but it is also failing.
<s:Panel id="colorPanel"
title="Dem display color"
width="500" height="500">
<s:layout>
<s:BasicLayout/>
</s:layout>
<s:Label id="label" y="4" horizontalCenter="0"/>
<s:BorderContainer id="Box1" x="70" y="70" height="50" width="50" backgroundColor="#0000ff">
</s:BorderContainer>
<s:BorderContainer id="Box2" x="90" y="90" height="51" width="50" backgroundColor="#00ff00">
</s:BorderContainer>
<s:BorderContainer id="Box3" x="50" y="50" height="52" width="50" backgroundColor="#ff0000">
</s:BorderContainer>
<s:Button label="Click" click="
colorPanel.setElementIndex(colorPanel.getElementAt(0),3);
label.text = ""+colorPanel.getElementAt(0).id ;
">
</s:Button>
</s:Panel>

Answer 1

Instead of casting to BorderContainer, it is safe to cast to UIComponent. In your example it crashes when the returned element is Label instead of BorderContainer. You can do as below:
<?xml version="1.0"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" xmlns:s="library://ns.adobe.com/flex/spark">
<fx:Script><![CDATA[
import mx.core.UIComponent;
]]></fx:Script>
<s:Panel id="colorPanel"
title="Dem display color"
width="500" height="500">
<s:layout>
<s:BasicLayout/>
</s:layout>
<s:Label id="label" text="Red" y="4" horizontalCenter="0"/>
<s:BorderContainer id="Blue" x="70" y="70" height="50" width="50" backgroundColor="#0000ff">
</s:BorderContainer>
<s:BorderContainer id="Green" x="90" y="90" height="51" width="50" backgroundColor="#00ff00">
</s:BorderContainer>
<s:BorderContainer id="Red" x="50" y="50" height="52" width="50" backgroundColor="#ff0000">
</s:BorderContainer>
<s:Button label="Click" click="{
colorPanel.setElementIndex(colorPanel.getElementAt(1),3);
label.text = UIComponent(colorPanel.getElementAt(3)).id;}"/>
</s:Panel>
</s:Application>

Answer 2

Solution I found seems like over rigidness on the part of Adobe. I was able to get value of Id the moment I casted the returned Element as BorderContainer. So we have to live with it till Adobe lowers it's compiler's expectations from us.
label.text = ""+ BorderContainer(colorPanel.getElementAt(0)).id ;