I am attempting to change the contentInsets property of a UITextView upon they keyboard showing, so that it is not hidden behind the keyboard. I have looked at a number of questions concerning this task, and have tried following the approved or highly voted answers, and have tried following Apple's recommended approach:
My code is currently as follows, in ViewDidLoad():
NSNotificationCenter.defaultCenter().addObserver(self, selector: "keyboardWillShow:", name: UIKeyboardWillShowNotification, object: nil)
the function that is indicated by the selector is:
func keyboardWillShow(notification : NSNotification){
    let info :NSDictionary = notification.userInfo! as NSDictionary;
    if let keyboardRect = info.objectForKey(UIKeyboardFrameEndUserInfoKey){
        var inset = commentsText.contentInset;
        inset.bottom = keyboardRect.size.height
        UIView.animateWithDuration(0.25, animations: {
            self.commentsText.contentInset = inset
        })
    }
}
commentsText is the name of the UITextView I am trying to adjust the innocence of. 
The problem I am having is that when attempting to access keyboardRect.size.heigh I have a fatal error of attempting to unwrap an unexpected nil value. I really am not sure how to fix this, because as far as I can tell I am following accepted answers and documentation (The animation block is an addition to Apple's documentation, but it is from an accepted answer, How do I resize views when keyboard pops up using Auto Layout , so I figure it probably isn't the source of the problem. 
I have also attempted using the UIKeyboardDidShowNotification as well as using the UIKeyboardFrameBeginUserInfoKey, but neither of those substitutions changed the error. 
The documentation from Apple and most questions/answers on this topic are in Objective-C, and while I think I correctly "translated" them into Swift for my purposes, it is entirely possible I made a mistake somewhere, if this is the case please let me know what my error was. 
Any help/suggestions would be appreciated.
Thanks in advance.
P.S. I am currently working in Xcode 7 Beta 6
 
     
    