Push text field up to prevent keyboard cover in table view

PushTextfieldUp.swift

override func viewWillAppear(animated: Bool) {
    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)
  }
  
  func keyboardWillShow(aNotification: NSNotification) {
    // Get the size of the keyboard.
    let info  = aNotification.userInfo
    let aValue = info?[UIKeyboardFrameEndUserInfoKey] as? NSValue
    let keyboardSize = aValue?.CGRectValue().size
    
    tableView.contentInset = UIEdgeInsetsMake(0, 0, keyboardSize!.height, 0)
    
    let voteCell = tableView.cellForRowAtIndexPath(NSIndexPath(forRow: 2, inSection: 0))
    if voteCell != nil {
      tableView.scrollRectToVisible(voteCell!.frame, animated: true)
    }
  }
  
  func keyboardWillHide(aNotification: NSNotification) {
    tableView.contentInset = UIEdgeInsetsMake(0, 0, 0, 0)
  }