I've run across some peculiar behavior and I am trying to figure out if I
should report it and if so, how exactly to explain it. Given these two bits
of code:
*TestObject.as:*
package
{
public class TestObject
{
[Bindable] public var a:uint = 2;
[Bindable] public var b:uint = 3;
[Bindable] public var x:uint = 1;
}
}
*Main Application:*
<?xml version="1.0" encoding="utf-8"?>
<Application
xmlns="http://www.adobe.com/2006/mxml";
>
<Script>
<![CDATA[
import mx.collections.ArrayCollection;
[Bindable] public var d:ArrayCollection = new ArrayCollection([
new TestObject,
new TestObject,
new TestObject
]);
]]>
</Script>
<List dataProvider="{d}">
<itemRenderer>
<Component>
<HBox>
<Label text="{TestObject(data).a}"/>
<Label text="{(data as TestObject).b}"/>
<Label text="{(data as TestObject).x}"/>
</HBox>
</Component>
</itemRenderer>
</List>
<Button click="for each (var o:TestObject in d) { o.x++; o.a++; o.b++ }"/>
</Application>
If you run this application, you get the following warnings:
warning: unable to bind to property 'b' on class
'GenericTest_inlineComponent1'
warning: unable to bind to property 'b' on class
'GenericTest_inlineComponent1'
warning: unable to bind to property 'b' on class
'GenericTest_inlineComponent1'
warning: unable to bind to property 'b' on class
'GenericTest_inlineComponent1'
warning: unable to bind to property 'b' on class
'GenericTest_inlineComponent1'
warning: unable to bind to property 'b' on class
'GenericTest_inlineComponent1'
There's a couple of things that stand out here. First, it doesn't complain
about properties "x" or "a". The reason it doesn't complain about property
"a" is that I used "TestObject(data).a" instead of "(data as
TestObject).a". If you change it to the other way around, you will get a
warning on "a" as well. I find this rather bizarre, as I thought there was
no functional difference to the two, other than "as" returning null if the
object wasn't of the appropriate type rather than just erroring out like
straight type coercion does. But type coercion/as are very (ahem) "lightly"
documented so I admit I don't know a lot. But I don't think it's because of
the null problem, since you can replace it with "TestObject(null).b" and it
stops giving the warning.
The second weird thing is that it doesn't complain about "x" when using
"(data as TestObject).x" like it does with a. As you can see, it's claiming
this error is on GenericTest_inlineComponent1. This is significant because
it appears that it's instead doing some binding to the "x" property on the
item renderer, which is *very* odd. You can try this yourself by changing
"x" to other strings. Ones where there is a property of HBox named the same
thing won't give you a warning. Others will.
Yet for all this griping, it seems the data binding IS working. If you
click on the button, you'll see all the labels in the list change as the
data is being changed.
So, anyone want to shed some light on these two behaviors?
--
Jason
