KeyboardAvoidable2.swift

//MARK: - Public
extension KeyboardAvoidable where Self: UIViewController {
    func setupKeyboardNotifications() {
        NotificationCenter.default.addObserver(forName: .UIKeyboardWillShow, object: nil, queue: nil, using: {
            [weak self] notification in
            //Had to use block because protocols don't understand selectors
            //Therefore whoever conforms to `KeyboardAvoidable` needs to call `removeKeyboardNotifications` in deinit
            self?.keyboardWillAppear(notification)
        })
        
        NotificationCenter.default.addObserver(forName: .UIKeyboardWillHide, object: nil, queue: nil, using: {
            [weak self] notification in
            //Had to use block because protocols don't understand selectors
            //Therefore whoever conforms to `KeyboardAvoidable` needs to call `removeKeyboardNotifications` in deinit
            self?.keyboardWillDisappear(notification)
        })
    }
    
    //Need to call this in deinit of ViewController
    func removeKeyboardNotifications() {
        NotificationCenter.default.removeObserver(self)
    }
}

//MARK: - Private
fileprivate extension KeyboardAvoidable where Self: UIViewController {
    func keyboardWillAppear(_ notification: Notification) {
      
    }
    
    func keyboardWillDisappear(_ notification: Notification) {

    }
}