Swift version: 5.6
iOS notifications are a simple and powerful way to send data in a loosely coupled way. That is, the sender of a notification doesn't have to care about who (if anyone) receives the notification, it just posts it out there to the rest of the app and it could be picked up by lots of things or nothing depending on your app's state.
As a basic example, you might want various parts of your app to do some work when the user logs in – you might want some views to refresh, you might want a database to update itself, and so on. To do this, just post a notification name like this:
let nc = NotificationCenter.default
nc.post(name: Notification.Name("UserLoggedIn"), object: nil)
Note: it is preferable, for type safety, to define your notification names as static strings that belong to a class or struct or other global form so that you don't make a typo and introduce bugs.
To register to catch a notification being posted, use this:
nc.addObserver(self, selector: #selector(userLoggedIn), name: Notification.Name("UserLoggedIn"), object: nil)
That will call a userLoggedIn()
method when your notification is posted.
SPONSORED Play is the first native iOS design tool created for designers and engineers. You can install Play for iOS and iPad today and sign up to check out the Beta of our macOS app with SwiftUI code export. We're also hiring engineers!
Sponsor Hacking with Swift and reach the world's largest Swift community!
Available from iOS 2.0
This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.
Link copied to your pasteboard.