Swift version: 5.2
By default Swift generates code that is only available to other Swift code, but if you need to interact with the Objective-C runtime – all of UIKit, for example – you need to tell Swift what to do.
That’s where the @objc
attribute comes in: when you apply it to a class or method it instructs Swift to make those things available to Objective-C as well as Swift code. So, any time you want to call a method from a UIBarButtonItem
or a Timer
, you’ll need to mark that method using @objc
so it’s exposed – both of those, and many others, are Objective-C code.
Don’t worry: if you forget to add @objc
when it’s needed, your code simply won’t compile – it’s not something you can forget by accident and introduce a bug.
To expose a method to Objective-C, just write @objc
before its name like this:
class MyController: UIViewController {
@objc func authenticateUser() {
}
}
That whole class is automatically Objective-C friendly because it inherits from UIViewController
, but if you need it you can also explicitly make a class open to Objective-C by marking it @objc
.
SPONSORED Would you describe yourself as knowledgeable, but struggling when you have to come up with your own code? Fernando Olivares has a new book containing iOS rules you can immediately apply to your coding habits to see dramatic improvements, while also teaching applied programming fundamentals seen in refactored code from published apps.
Sponsor Hacking with Swift and reach the world's largest Swift community!
Available from iOS 8.0
This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.
Link copied to your pasteboard.