             objc_setAssociatedObject(self, _currentImageKey, newValue, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN);
         }
     }
-
+    
     private var displayOrderIndex:Int{
         get {
             return (objc_getAssociatedObject(self, _displayOrderIndexKey) as! Int)

            objc_setAssociatedObject(self, _displayOrderIndexKey, newValue, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN);
        }
    }

    private var syncFactor:Int{
        get {
            return (objc_getAssociatedObject(self, _syncFactorKey) as! Int)

            objc_setAssociatedObject(self, _displayingKey, newValue, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN);
        }
    }
    
    private var cache:NSCache{
        get {
            return (objc_getAssociatedObject(self, _cacheKey) as! NSCache)
