键盘显示时我有这个错误的崩溃：

2014-09-29 14：48：50.738 swrd [1563：472888] – [swrd.EditPhotoViewController keyboardWasShown]：无法识别的选择器发送到实例0x14ed36640

这是我的代码,怎么了？

func registerForKeyboardNotifications ()-> Void   {
 
    NSNotificationCenter.defaultCenter().addObserver(self,selector: "keyboardWasShown",name: UIKeyboardDidShowNotification,object: nil)
 
    NSNotificationCenter.defaultCenter().addObserver(self,selector: "keyboardWillBeHidden",name: UIKeyboardWillHideNotification,object: nil)
 
 
}
 
func deregisterFromKeyboardNotifications () -> Void {
    let center:  NSNotificationCenter = NSNotificationCenter.defaultCenter()
    center.removeObserver(self,name: UIKeyboardDidHideNotification,object: nil)
    center.removeObserver(self,object: nil)
 
 
}
 
 
 func keyboardWasShown (notification: NSNotification) {
 
    let info : NSDictionary = notification.userInfo!
    let keyboardSize = info.objectForKey(UIKeyboardFrameBeginUserInfoKey)?.frame
 
    let insets: UIEdgeInsets = UIEdgeInsetsMake(self.scrollView.contentInset.top,keyboardSize!.height,0)
 
    self.scrollView.contentInset = insets
    self.scrollView.scrollIndicatorInsets = insets
 
    self.scrollView.contentOffset = CGPointMake(self.scrollView.contentOffset.x,self.scrollView.contentOffset.y + keyboardSize!.height)
 
}
 
func keyboardWillBeHidden (notification: NSNotification) {
 
    let info : NSDictionary = notification.userInfo!
    let keyboardSize = info.objectForKey(UIKeyboardFrameBeginUserInfoKey)?.frame
 
    let insets: UIEdgeInsets = UIEdgeInsetsMake(self.scrollView.contentInset.top,0)
 
    self.scrollView.contentInset = insets
    self.scrollView.scrollIndicatorInsets = insets
 
 
 
}
 
 
 override func viewWillAppear(animated: Bool) {
    super.viewWillAppear(true)
 
 
 
   self.registerForKeyboardNotifications()
 
}
 
 override func viewWillDisappear(animated: Bool) {
    super.viewWillDisappear(true)
 
    self.deregisterFromKeyboardNotifications()
 
}