Swift：对ViewController进行子类化并添加目标？

I am creating an app with swift and I subclassed a view controller in which I add a tap gesture recognizer and an NSNotification that listens for the keyboard appearing. I put the selector for the keyboardWillShow in a function in my base view controller. When I subclassed my view controller, however, and I had the keyboard show, my app terminated with an NSException that said that it could not find the selector. Can anyone explain why this happened and how I can fix it? I am creating an app with swift and I subclasse