Can't call Swift function from Objective-C

Question

I have this static function in a Swift class that I'd like to call in Objective-C:

static internal func photoActionSheet<T:UIViewController where T:UIImagePickerControllerDelegate, T:UINavigationControllerDelegate>(hostAndDelegateViewController:T)

I have other functions from the class that I'm able to call from ObjC, but it doesn't know of just this one

Thanks

Nope...the other functions are internal as well and they're ok. — theNotSoPro
– theNotSoPro, Commented Nov 24, 2015 at 8:36
I'd appreciate it if you would remove that downvote. I'm trying to build up my rep :) — theNotSoPro
– theNotSoPro, Commented Nov 24, 2015 at 8:48

世人都晓神仙好 · Accepted Answer · 2015-11-24 08:58:51Z

2

Functions with generic type constraints cannot be exported to Objective-C.

As a workaround, you could define the function like below and check for protocol conformance inside the function implementations:

static internal func photoActionSheet(hostAndDelegateViewController: UIViewController) {
  guard let vc = hostAndDelegateViewController as? protocol<UINavigationControllerDelegate, UIImagePickerControllerDelegate> else {
    fatalError("hostAndDelegateViewController must conform UINavigationControllerDelegate and UIImagePickerControllerDelegate")
  }

  // let picker = UIImagePickerController()
  // picker.delegate = vc
}

Likewise, Objective-C type UIViewController<UIImagePickerControllerDelegate, UINavigationControllerDelegate> * will be exported to Swift as UIViewController!

edited Nov 24, 2015 at 8:58

answered Nov 24, 2015 at 8:47

世人都晓神仙好

3,5953 gold badges27 silver badges49 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

theNotSoPro Over a year ago

Good to know. However, if I define the Swift function like what you did, I wouldn't be able to assign the UIViewController as a delegate of a UIImagePickerController (because it needs the two protocols) correct?

世人都晓神仙好 Over a year ago

@theNotSoPro It can be done with a type cast trick. I've updated my answer.

Collectives™ on Stack Overflow

Can't call Swift function from Objective-C

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related