     private let kAddMargin:CGFloat = 10
     private let kMinFieldWidth:CGFloat = 15
     private let kMaxFieldWidth:CGFloat = 160
+    private let kMinConfirmWidth:CGFloat = 0
+    private let kMaxConfirmWidth:CGFloat = 100
     
     override init(frame:CGRect)
     {

                { [weak self] in
                    
                    self?.layoutIfNeeded()
                })
            { [weak self] (done:Bool) in
                
                self?.field.textField.becomeFirstResponder()
            }
        }
    }

        layoutAddLeft.constant = kAddMargin
        
        let maxFieldWidth:CGFloat = kMaxFieldWidth
        let maxConfirmWidth:CGFloat = kMaxConfirmWidth
        let animationDuration:TimeInterval = kAnimationDuration
        
        UIView.animate(
