Set.as

package jubishop {
  import mx.collections.ArrayCollection;
  
  public class Set extends ArrayCollection {
    public function removeItem(item:Object):int {
      var itemIndex:int = getItemIndex(item);
      if (itemIndex == -1) return -1;
      removeItemAt(itemIndex);
      return itemIndex;
    }
    
    public override function addItem(item:Object):void {
      removeItem(item);
      super.addItem(item);
    }
    
    public override function addItemAt(item:Object, index:int):void {
      if (getItemIndex(item) == index) return;
      var removedIndex:int = removeItem(item);
      if (removedIndex != -1 && removedIndex < index) index--;
      super.addItemAt(item, index);
    }
    
    public override function setItemAt(item:Object, index:int):Object {
      if (getItemIndex(item) == index) return item;
      var removedIndex:int = removeItem(item);
      if (removedIndex != -1 && removedIndex < index) index--;
      return super.setItemAt(item, index);
    }
  }
}