Flex Tree Folder/File Leaf/Branch icons

Question

Hello Everyone ,
  I have an object which implements ITreeDataDescriptor and I stuff the objects into a Tree.  The objects are being shown in the tree , however  , they are all shown with the folder icon.  Is there a way I can tell this tree that some things should be represented by folders and that others should be represented by files ?  I have attached the disastrous code.  It has everything you need to see the damage. In the xml , the nodes are either labeled "Directory" , "Topdirectory" or "File"
P.S
For some reason the adobe flex forum wont let me attach ... Flex files ?  Here is the FileModel that implements the ITreeDataDescriptor and the tree mxml
Tree mxml
<mx:Tree id="Tree" itemClick="{thingClicked(event)}" labelField="name" width="100%" height="100%" dataProvider="{collection}" />
FileModel.as
package {
    import flash.events.EventDispatcher;
    import flash.events.IEventDispatcher;
    import mx.collections.ArrayCollection;
    import mx.collections.ICollectionView;
    import mx.controls.treeClasses.ITreeDataDescriptor;
    import mx.core.IUID;
    public class FileModel extends EventDispatcher implements ITreeDataDescriptor, IUID
        public var userId:String;
        public var name:String;
        public var fileId:String;
        public var parentId:String;
        public var modified:String;
        public var description:String;
        public var type:String;
        public var children:ArrayCollection;
        public function FileModel(target:IEventDispatcher=null)
            super(target);
            children = new ArrayCollection();
        public function getChildren(node:Object, model:Object=null):ICollectionView
            return children;
        public function hasChildren(node:Object, model:Object=null):Boolean
            if(children.length > 0)
            {return true;}
            else
            {return false;}
        public function isBranch(node:Object, model:Object=null):Boolean
             if(type == "DIRECTORY" || type=="TOPDIRECTORY")
            {return true;}
            else
            {return false;}
        public function getData(node:Object, model:Object=null):Object
            return this;
        public function addChildAt(parent:Object, newChild:Object, index:int, model:Object=null):Boolean
            return false;
        public function removeChildAt(parent:Object, child:Object, index:int, model:Object=null):Boolean
            return false;
        public function get uid():String
            return fileId;
        public function set uid(value:String):void
        public function addChild(childModel:FileModel):void
            children.addItem(childModel);

Answer 1

Thanks pm.  I finally got it to work.  Apparently the functions implemented when using ITreeDataDescriptor don't always make sense.  To get something to be seen as a leaf and not a branch.  item.isBranch can't be the only to show false.  The item.getChildren call must also return a null ICollectionView or something crazy like that , otherwise , your leaves will have disclosure symbols beside them.