HierarchicalCollectionView updateLength discovery

So, in another round of heavy debugging - I came across an an anomaly, which really is just a difference between what the developer thought would happen, and how I chose to implement a feature.

In the HierarchicalCollectionView, on the collectionChange event the length of the collection gets updated for nearly all CollectionChangeKinds except for UPDATE. Now this makes sense, changing a property shouldn't result in a change of length (like adding or removing children).

Unfortunately, the way that I a structured our application was that the items that needed to expand (ie have children) where flat, not hierarchical. So my solution was to toggle a property on the item to indicate that it had children. When I applied the same interface to the grouping collections (so that I could use the same framework for expanding and collapsing), I discovered that the length wasn't being recalculated and thus scrolling was throw off.

Annoyingly, much of the calculate length features in HierarchicalCollectionView are private. So here is a solution that I put in place, but it isn't very pretty:

class HierarchicalCollectionViewWithUpdateListeners extends HierarchicalCollectionView
{
 
 private var myLength:int
 private const NO_LENGTH:int  = -1
 public function HierarchicalCollectionViewWithUpdateListeners(hierarchicalData:IHierarchicalData=null, argOpenNodes:Object=null)
 {
  super(hierarchicalData, argOpenNodes);
 }
 
 
  public override function collectionChangeHandler(event:CollectionEvent):void
  {
   super.collectionChangeHandler(event);
   myLength = NO_LENGTH;
   if (event.kind == CollectionEventKind.UPDATE)
   {
    myLength = calculateLength();
   }
   
  }

  
  public override function get length():int
  {
   var origLen:int = super.length;
   if (myLength != NO_LENGTH)
   {
    return myLength;
   }
   else
   {
    return origLen; 
   }
  }


}