Swift - resignFirstResponder resets contentOffset on my UITextView. How come? - swift

Question

So I have a pretty simple app I am trying to build. Its basically a scrollable text field that fills up the entire screen.
When the user taps the screen, the keyboard appears and you can begin to edit on the line where you tapped.
If you tap in the area where the keyboard is going to appear, the size of the textView shrinks so you aren't entering text behind the keyboard.
Everything up until here works. Ill put the code at the bottom.
When the user is done editing, there is a 'Done' button in the upper right hand of the screen, When they press that, the keyboard should disappear, and, if the amount of text is more than what fits on the screen, whichever line they were editing should be at the bottom of the screen.
Right now, no matter what I try, when I resignFirstResponder to hide the keyboard, the textView resets the contentOffset to (0,0)
When I am in the above view, I press done, and this is the result:
what I would like to happen is where I was editing to be at the bottom of the screen, like this:
Class variables so they can be accessed from anywhere in the file
var textField: UITextView = UITextView()
var withKeyboard: NSLayoutConstraint!
var withoutKeyboard: NSLayoutConstraint!
override func viewDidLoad() {
super.viewDidLoad()
self.view.addSubview(textField)
textField.scrollEnabled = true
textField.selectable = true
textField.bounces = true
textField.contentMode = UIViewContentMode.Bottom
textField.setTranslatesAutoresizingMaskIntoConstraints(false)
self.withoutKeyboard = NSLayoutConstraint(item: self.textField, attribute: NSLayoutAttribute.Bottom, relatedBy: NSLayoutRelation.Equal, toItem: self.view, attribute: NSLayoutAttribute.Bottom, multiplier: 1, constant: 0)
self.view.addConstraint(NSLayoutConstraint(item: self.textField, attribute: NSLayoutAttribute.Top, relatedBy: NSLayoutRelation.Equal, toItem: self.view, attribute: NSLayoutAttribute.Top, multiplier: 1, constant: 0))
self.view.addConstraint(self.withoutKeyboard)
self.view.addConstraint(NSLayoutConstraint(item: self.textField, attribute: NSLayoutAttribute.Left, relatedBy: NSLayoutRelation.Equal, toItem: self.view, attribute: NSLayoutAttribute.Left, multiplier: 1, constant: 0))
self.view.addConstraint(NSLayoutConstraint(item: self.textField, attribute: NSLayoutAttribute.Right, relatedBy: NSLayoutRelation.Equal, toItem: self.view, attribute: NSLayoutAttribute.Right, multiplier: 1, constant: 0))
}
func keyboardWillShow(notification: NSNotification){
doneButton.hidden = false
if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.CGRectValue() {
keyboardHeight = keyboardSize.height
self.withKeyboard = NSLayoutConstraint(item: self.textField, attribute: NSLayoutAttribute.Bottom, relatedBy: NSLayoutRelation.Equal, toItem: self.view, attribute: NSLayoutAttribute.Bottom, multiplier: 1, constant: -keyboardHeight)
self.view.removeConstraint(withoutKeyboard)
self.view.addConstraint(withKeyboard)
textField.layoutIfNeeded()
}
}
func keyboardWillHide(notification: NSNotification){
self.doneButton.hidden = true
self.textFieldOffset = self.textField.contentOffset.y - self.keyboardHeight
println(self.textFieldOffset)
self.view.removeConstraint(withKeyboard)
self.view.addConstraint(withoutKeyboard)
textField.layoutIfNeeded()
textField.contentOffset.y = self.textFieldOffset
}
func donePressed(){
textField.resignFirstResponder()
createRecord()
}
I made the withKeyboard and withoutKeyboard constraints so that I could take one off and add the other one whenever the keyboard appears/disappears.
Anyway, when I hit the done button, it resets the view to the very top. This isnt all of the code, its just the parts that are giving me trouble.