         self.view.addSubview(targetView)
         targetView.removeButton.target = self
         targetView.removeButton.action = Selector("removeTargetView:")
-        self.targetViews?.addObject(targetView)
+        self.targetViews?.append(targetView)
         self.arrangeTargetViews()
         self.addButton.enabled = self.shouldAddTarget()
     }

    {
        for var i = self.targetViews!.count - 1; i >= 0; i--
        {
            let targetView = self.targetViews!.objectAtIndex(i) as! TargetView
            
            targetView.snp_remakeConstraints { (make) -> Void in
                let upperView: NSView!

                }
                else
                {
                    upperView = self.targetViews![i - 1]
                }
                
                make.centerY.equalTo(upperView.snp_centerY).offset(40.0)
