UIKeyboardWillHide has been renamed to UIResponder.keyboardWillHideNotification

//4.0
Notification.Name.UIKeyboardWillHide
//change to
//4.2
UIResponder.keyboardWillHideNotification
//4.0
Notification.Name.UIKeyboardWillChangeFrame
//4.2
UIResponder.keyboardWillChangeFrameNotification
//4.0
Notification.Name.UIApplicationWillResignActive
//4.2
UIApplication.willResignActiveNotification
//4.0
let keyboardScreenEndFrame = (userInfo[UIKeyboardFrameEndUserInfoKey] as! NSValue).cgRectValue
//4.2
  let keyboardScreenEndFrame = (userInfo[UIResponder.keyboardFrameEndUserInfoKey] as! NSValue).cgRectValue