             attachmentBehavior.frequency = 1.0
             
             attachmentBehaviors[id] = attachmentBehavior
-                
+            
+            print("---------------------")
+            for behavior in dynamicAnimator.behaviors {
+                printBehaviorHierachy(behavior, indent: "==>")
+            }
+            
             dynamicAnimator.addBehavior(attachmentBehavior)
+
             gravityBehavior.addItem(attributes)
-            collisionBehavior.addItem(attributes)
+//            collisionBehavior.addItem(attributes)
         }
         
         if change {

    }
    
    func fixTheIndexPathForLayoutAttributes() {
        print("behaviors : \(dynamicAnimator.behaviors.count)")
        print("gravity : \(gravityBehavior.items.count)")
        print("collision : \(collisionBehavior.items.count)")
        let dataSource = collectionView!.dataSource as! NewtownianCollectionViewDataSource
        for behavior in attachmentBehaviors.values {
            let attribute = behavior.items.first as! NewtownianLayoutAttributes

    lazy var dynamicAnimator : UIDynamicAnimator = { [unowned self] in
        let result = UIDynamicAnimator(collectionViewLayout: (self as UICollectionViewFlowLayout))
        result.addBehavior(self.gravityBehavior)
//        result.addBehavior(self.collisionBehavior)
        return result
    }()
    
