title: Swift can't convert the expression's type '()' to type CGRect
body: <p>I am new in Swift, and I am trying to animate textField because my keyboard hides it. 
  In objective-c this code worked great. 
  Here is the editing did begin event function:</p>
  
  <pre><code>@IBAction func passwordEditingBegin(sender : UITextField) {
      var movementDistance:Int = 50
      var movementDuration = 0.3
  
      UIView.beginAnimations("anim", context: nil)
      UIView.setAnimationBeginsFromCurrentState(true)
      UIView.setAnimationDuration(movementDuration)
  
  
  
      self.view.frame = CGRectOffset(self.view.frame, 0, movementDistance)
                      //^ Can't convert the expressions type '()' to type CGFloat
      UIView.commitAnimations()
  }
  </code></pre>