Why are my XMLListCollection properties in my custom components always null?

Question

I've written the following custom component, SubNavBar.mxml:

<?xml version="1.0" encoding="utf-8"?>
<mx:Canvas xmlns:mx="http://www.adobe.com/2006/mxml" height="100" width="300"
 creationComplete="init()">

 <mx:Script>
  <![CDATA[
   import mx.collections.XMLListCollection;

   [Bindable] public var menuItems:XMLListCollection;

   private function init():void
   {
    trace("SubNav: config = "+menuItems);
   }


  ]]>
 </mx:Script>

 <mx:HBox y="30" id="menu">
  <mx:List dataProvider="{menuItems}"/>
 </mx:HBox>

</mx:Canvas>

I setup this component in a parent custom component using the following code:

<com:SubNavBar id="subNavMenu" menuItems="{subNavConfig}"
 x="10" y="-15">
</com:SubNavBar>

Whenever the trace function runs in init(), the property menuItems returns null. I don't seem to have this problem with other variable types, like Boolean or String. Is this due to the size of the XMLListCollection object? How can I set up this SubNavBar custom component with XMLListCollection property and bind it to a control in the component?

Thanks!

Answer 1

I tested out this code and everything seemed to work for me. Are you sure you're setting up the subNavConfig variable properly?

Here's the client code I used:

// Test.mxml

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" initialize="onInit()" xmlns:ns="comp.*">
  <mx:Script>
    <![CDATA[
      import mx.collections.XMLListCollection;

      [Bindable]
      public var bookCollection:XMLListCollection;

      public function onInit():void
      {
        var books:XML = <books>
                          <book publisher="Addison-Wesley" name="Design Patterns" />
                          <book publisher="Addison-Wesley" name="The Pragmatic Programmer" />
                          <book publisher="Addison-Wesley" name="Test Driven Development" />
                          <book publisher="Addison-Wesley" name="Refactoring to Patterns" />
                          <book publisher="O'Reilly Media" name="The Cathedral & the Bazaar" />
                          <book publisher="O'Reilly Media" name="Unit Test Frameworks" />
                        </books>;

        var booklist:XMLList = books.book;
        bookCollection = new XMLListCollection(booklist);
      }
    ]]>
  </mx:Script>

  <ns:SubNavBar id="fb" menuItems="{bookCollection}"/>
</mx:Application>

And here's the output I got:

SubNav: config = <book publisher="Addison-Wesley" name="Design Patterns"/>
<book publisher="Addison-Wesley" name="The Pragmatic Programmer"/>
<book publisher="Addison-Wesley" name="Test Driven Development"/>
<book publisher="Addison-Wesley" name="Refactoring to Patterns"/>
<book publisher="O'Reilly Media" name="The Cathedral &amp; the Bazaar"/>
<book publisher="O'Reilly Media" name="Unit Test Frameworks"/>

Answer 2

Maybe I am missing something, but where are you setting {subNavConfig} ?

Edit:

It could be because of how it is being casted...try something like...

var listcol:XMLListCollection = new XMLListCollection(configXML.destination.(@mapID == mapID).subSections);