override func viewWillAppear(animated: Bool) {
  super.viewWillAppear(animated)

  NSNotificationCenter.defaultCenter().addObserver(self,
    selector: "keyboardWillShow:",
    name: UIKeyboardWillShowNotification,
    object: nil)
  NSNotificationCenter.defaultCenter().addObserver(self,
    selector: "keyboardWillHide:",
    name: UIKeyboardWillHideNotification,
    object: nil)
}

override func viewWillDisappear(animated: Bool) {
  NSNotificationCenter.defaultCenter().removeObserver(self,
    name: UIKeyboardWillShowNotification,
    object: nil)
  NSNotificationCenter.defaultCenter().removeObserver(self,
    name: UIKeyboardWillHideNotification,
    object: nil)

  super.viewWillDisappear(animated)
}

func keyboardWillShow(notification: NSNotification) {
  if let userInfo = notification.userInfo {
    let value = userInfo[UIKeyboardFrameEndUserInfoKey] as! NSValue
    let rect = value.CGRectValue()

    UIView.animateWithDuration(0.3,
      animations: { [unowned self] () -> Void in
        var frame = self.view.frame
        frame.origin.y = -(rect.origin.y / 4)
        self.view.frame = frame
    })
  }
}

func keyboardWillHide(notification: NSNotification) {
  UIView.animateWithDuration(0.4,
    animations: { [unowned self] () -> Void in
      var frame = self.view.frame
      frame.origin.y = 0.0
      self.view.frame = frame
  })
}