move hidden text fields up if keyboard appears

ViewUp.swift

    public override func viewWillAppear(animated: Bool) {
        super.viewWillAppear(animated)
        NSNotificationCenter.defaultCenter().addObserver(self, selector: "keyBoardWillShow:", name: UIKeyboardDidShowNotification, object: nil)
        NSNotificationCenter.defaultCenter().addObserver(self, selector: "keyBoardWillHide:", name: UIKeyboardDidHideNotification, object: nil)
    }
    
    public override func viewDidDisappear(animated: Bool) {
        super.viewDidDisappear(animated)
        NSNotificationCenter.defaultCenter().removeObserver(self)
    }
    
    //MARK: handling hidden textfields
    public func textFieldDidBeginEditing(textField: UITextField) {
        activeTextField = textField
    }
    
    public func textFieldDidEndEditing(textField: UITextField) {

    }
    
    public func textFieldShouldReturn(textField: UITextField) -> Bool {
        textField.resignFirstResponder()
        return true
    }
    
    func keyBoardWillShow(notification: NSNotification){
        if let size = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.CGRectValue() {
            keyboardSize = size
        }
        moveUp()
    }
    
    func keyBoardWillHide(notification: NSNotification){
        moveDown()
    }
    
    func moveUp(){
        if view.frame.origin.y == 0 {
            let textFeldOriginBottom = activeTextField!.frame.origin.y + addressTextField.frame.height
            let position = view.frame.height - textFeldOriginBottom
            let offset = position - keyboardSize!.height
            if offset < 0 {
                var frame = view.frame
                frame.origin.y = offset - 8
                UIView.animateWithDuration(0.28, animations: { () -> Void in
                    self.view.frame = frame
                })
            }
        }
    }
    
    func moveDown(){
        if view.frame.origin.y != 0 {
            var frame = self.view.frame
            frame.origin.y = 0
            UIView.animateWithDuration(0.28, animations: { () -> Void in
                self.view.frame = frame
            })
        }
    }