<?xml version="1.0" encoding="utf-8"?>

<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"

                layout="vertical"

                verticalAlign="middle"

                backgroundColor="white">

    <mx:Script>

        <![CDATA[

            import mx.controls.ButtonBar;

            private var buttonBarXML:XML = describeType(ButtonBar);

            private function buttonBar_labelFunc(item:Object):String {

                var cat:String = item.category.toUpperCase();

                var len:uint = buttonBarXML.factory.child(item.data).length();

                return cat + " (" + len + ")";

            }

        ]]>

    </mx:Script>

    <mx:Array id="arr">

        <mx:Object category="Accessors" data="accessor" />

        <mx:Object category="Methods" data="method" />

    </mx:Array>

    <mx:ButtonBar id="buttonBar"  dataProvider="{arr}"  labelFunction="buttonBar_labelFunc" />

</mx:Application>