Custom Components and Properties in Flex Builder Design View

Question

How do I create a custom component with custom properties
that renders well in Flex Builder design view?
This is a simple HelloWorld example of what I am trying
below. Here is the HelloWorld.mxml file:
<?xml version="1.0" encoding="utf-8"?>
<mx:Canvas xmlns:mx="
http://www.adobe.com/2006/mxml"
width="500" height="500">
<mx:Script><![CDATA[
[Bindable]
public var message:String;
]]></mx:Script>
<mx:Label x="100" y="100" text="{message}" />
</mx:Canvas>
And then when I use it in another mxml file, the design view
does not show the label with the 'Hello World' value - instead it
just shows {message} in design view where the label is located.
When I run it as a compiled app in flash, the 'Hello World' is
displayed correctly:
-- HelloWorldTest.mxml --
<?xml version="1.0" encoding="utf-8"?>
<mx:Canvas xmlns:mx="
http://www.adobe.com/2006/mxml"
xmlns:views="mypackage.*" width="500" height="500">
<views:SimpleLine message="Hello World."/>
</mx:Canvas>

Answer 1

design view does not do any variable assignments or function
evaluations, so you won't be able to see it even if you don't use a
custom component.