Using #objc in Swift 5 protocols - ios

Question

I have an issue with using #objc code in swift protocols and was wondering if there is a workaround for that.
Currently, I have code:
import UIKit
#objc
protocol TrackScreenshot {
func registerObserver()
func removeObservers()
}
extension TrackScreenshot where Self: ScreenTracking {
func registerObserver() {
NotificationCenter.default.addObserver(self, selector: #selector(trackScreenshot), name: UIApplication.userDidTakeScreenshotNotification, object: nil)
}
func removeObservers() {
NotificationCenter.default.removeObserver(self, name: UIApplication.userDidTakeScreenshotNotification, object: nil )
}
func trackScreenshot() {
print(screenName.rawValue)
}
}
So I want to inherit the TrackScreenshot protocol and make screens easily trackable.
BUT there is an issue.
registerObserver() method on #selecor asks to add #objc to trackScreenshot method, but if I do so, Xcode complains on trackScreenshot() line and telling: #objc can only be used with members of classes, #objc protocols, and concrete extensions of classes
Is there a way to fix this?
Also tried:
NotificationCenter.default.addObserver(forName: UIApplication.userDidTakeScreenshotNotification, object: nil, queue: nil) { _ in
print(self.screenName.rawValue)
}
but it's not working, and the observer can't be removed and remains in the circle, so prints all the previous screen names when a new screen is opened.
Any help is more then welcome! Thanks in advance!

Answer 1

I would use the closure form of notification observation rather than a selector/method:
protocol TrackScreenshot {
func registerObserver(handler: (()->Void)?)
func removeObservers()
}
extension TrackScreenshot where Self: ScreenTracking {
func registerObserver(handler: (()->Void)?) {
NotificationCenter.default.addObserver(forName: UIApplication.userDidTakeScreenshotNotification, object: nil, queue: nil) { (notification) in
handler?()
}
}
func removeObservers() {
NotificationCenter.default.removeObserver(self, name: UIApplication.userDidTakeScreenshotNotification, object: nil )
}
}
Then your use is something like:
self.registerObserver { [weak self] in
guard let self = self else {
return
}
print("Screen shot")'
}

Answer 2

You can track screenshot notification using delegates too, feel free to refactor as per your need:
public protocol ScreenshotDelegate: AnyObject {
func screenshotDetected()
}
open class ScreenshotTracker: NSObject {
private weak var delegate: ScreenshotDelegate?
public init(delegate: ScreenshotDelegate) {
self.delegate = delegate
NotificationCenter.default.addObserver(forName: UIApplication.userDidTakeScreenshotNotification, object: nil, queue: OperationQueue.main) { notification in
delegate.screenshotDetected()
print("Screenshot notification")
}
}
}
ViewController Setup:
override func viewDidLoad() {
super.viewDidLoad()
let _ = ScreenshotTracker(delegate: self)
}
extension ViewController: ScreenshotDelegate {
func screenshotDetected() {
print("screenshot taken!!!")
}
}