Expose Objective C Class Extension Property in Swift

Question

Say I have the following in an Objective C implementation file (MyVC.m):

@interface MyVC ()
  @property (nonatomic, weak) IBOutlet UILabel *titlelabel;
@end

How can I expose this private property to Swift (test) code? The following causes compiler errors:

extension LTConversationSelectionVC {
   @IBOutlet weak var assetBar: LTAssetBar?
}

Answer 1

Unfortunately, there isn't a way to do this purely with Swift. However, you can expose the property in an Objective-C file in your test target and then put that in your test target's bridging header.

Add MyVC+Tests.h to your test target:

@interface MyVC (Tests)
  @property (nonatomic, weak) IBOutlet UILabel *titlelabel;
@end

MyAppTests-Bridging-Header.h

#import "MyVC+Tests.h"

Then, in your Swift code in the test target, you can use the titleLabel property as expected.

let vc = MyVC()
vc.titleLabel.text = "Hello, world!"

Answer 2

From apple doc

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Extensions can add new computed properties, but they cannot add stored properties, or add property observers to existing properties.

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Apple documentation Link here

Answer 3

You can do the same property-in-category trick from the Bridging Header file. Just forward any class that calls swift library. That should take care of the problem.