How to check that user is back from Settings - ios

Question

I am sending local notifications to my users, and I want to show the relevant title on the notification settings button.
If local notifications are off, this title should be "Notifications: off", and if local notifications are on, this title should be something like "Preferences".
Right now I'm checking this in viewDidLoad and viewDidAppear, and it works.
if UIApplication.sharedApplication().currentUserNotificationSettings()?.types.rawValue == 0 {
//the first title
} else {
//the second title
}
Except one case. If my user is changing notifications in the phone settings from "on" to "off" or vice versa, and after that he is back — the title is not changing (because this viewController already loaded and did appear).
How could I check that user is back from the Settings?

Answer 1

You can observe this notification when your app is come to foreground from inactive, the selector will be called everytime your app is opened again from background:
Put in viewDidLoad:
NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(self.reloadData), name: UIApplicationWillEnterForegroundNotification, object: UIApplication.sharedApplication())
Put in viewDidDissapear or deinit:
NSNotificationCenter.defaultCenter().removeObserver(self)

Answer 2

Swift 5.5:
NotificationCenter.default.addObserver(
self,
selector: #selector(yourFunction),
name: UIApplication.willEnterForegroundNotification,
object: UIApplication.shared
)
And:
deinit {
NotificationCenter.default.removeObserver(self)
}