Error with notification names while converting code to Swift 4.2

Question

The code below was working fine before Swift 4.2:

NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillChange(notification:)), name: NSNotification.Name.UIKeyboardWillShow, object: nil)

When I click the 'Fix' option, it becomes:

NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillChange(notification:)), name: NSNotification.Name.UIResponder.keyboardWillShowNotification, object: nil)

But it is still marked an error. Here is the explanation:

Type 'NSNotification.Name' has no member 'UIResponder'

And then I tried to delete 'UIResponder':

NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillChange(notification:)), name: NSNotification.Name.

...but I don't know how should I complete it.

Solution 1

The correct form is:

UIResponder.keyboardWillShowNotification

...so, your code becomes:

NotificationCenter.default.addObserver(
    self, 
    selector: #selector(keyboardWillChange(notification:)), 
    name: UIResponder.keyboardWillShowNotification, 
    object: nil
)

This is a known issue with Xcode 10. Automatic Fix-it is not working correctly for Swift 4.2 when it comes to correcting notification names.

In Swift 4.2, lots of Notification.Name instances became instance variables in other classes. For example, keyboardWillShowNotification is now an instance variable of UIResponder.

Solution 2

For someone else out there, I was building (what I thought was) a UI-Independent class and did not import UIKit.

Nothing worked until I added at the top of my file, this:

import UIKit

It appears some notifications (those in UIApplication, UIResponder etc..) may have been refactored into UIKIt.

Comments

[mannyCalavera]

I didn't know this: ' Automatic Fix-it is not working correctly for Swift 4.2 when it comes to correcting notification names.' (Thanks a lot)

[Raviteja Mathangi]

No luck for this code ....Implemented this code in UIWindow class "NotificationCenter.default.addObserver(self, selector: #selector(self.bringWindow(toTop:)), name: UIWindow.didBecomeVisibleNotification, object: nil)"

[Sazzad Hissain Khan]

Getting Cannot invoke 'addObserver' with an argument list of type '(RegistrationViewController, selector: Selector, name: NSNotification.Name)'

[Tamás Sengel]

@SazzadHissainKhan Sorry about that, Madhu_Nani was right - object: nil was missing. I've edited my post