NSNotfication.addObserver - Update to current Swift Syntax?

Question

Currently following a tutorial, however, some of the syntax is outdated. Basically the code should show and hide the user keyboard. I get some syntax errors with the addObserver method and Swift wants me to use key path instead, however, if i use the auto 'fix-it' i get even more errors. Can anyone help me out with this? Thanks!

NSNotification.addObserver(self, selector: #selector(keyboardwillShow), name: .UIKeyboardWillShow, nil)       
NSNotification.addObserver(self, selector: #selector(keyboardwillHide), name: .UIKeyboardWillHide, nil)


func keyboardwillShow(_notification:NSNotification) {    
    keyboard = (_notification.userInfo![UIKeyboardFrameEndUserInfoKey]! as AnyObject).cgRectValue
    UIView.animate(withDuration: 0.4) { 
        self.scrolledView.frame.size.height = self.scrollViewHeight - self.keyboard.height
    }
}

func keyboardwillHide(_notification:NSNotification) {
    UIView.animate(withDuration: 0.5) { 
        self.scrolledView.frame.size.height = self.view.frame.height
    }
}

I get the debug message: "Incorrect argument labels in call(have _selector:name, expected _forKeyPath:options:context"

Answer 1

Your function has argument, That is missing when you add it in observer

And you have to use NotificationCenter.default.addObserver not NotificationCenter.addObserver

let selectorForKeyBoardWillShow: Selector = #selector(ViewController.keyboardWillShow(_:))
let selectorForKeyBoardWillHide: Selector = #selector(ViewController.keyboardWillHide(_:))

    // MARK: - Functions
override func viewDidLoad() {
    super.viewDidLoad()
    NotificationCenter.default.addObserver(self, selector: selectorForKeyBoardWillShow, name: NSNotification.Name.UIKeyboardWillShow, object: nil)
    NotificationCenter.default.addObserver(self, selector: selectorForKeyBoardWillHide, name: NSNotification.Name.UIKeyboardWillHide, object: nil)
}


// MARK: Keyboard Observer
func keyboardWillShow(_ notification: Notification) {
}

func keyboardWillHide(_ notification: Notification) {
}