iosswiftxcode16

Cannot Extend UIApplication to Conform to Custom Protocol in Xcode 16

I am trying to extend UIApplication to conform to a custom protocol AppSwitcher for handling URL opening. This code worked fine in Xcode 15, but after upgrading to Xcode 16, it is causing errors.

public protocol AppSwitcher {
    func open(
        _ url: URL,
        options: [UIApplication.OpenExternalURLOptionsKey: Any],
        completionHandler completion: ((Bool) -> Void)?
    )
}

extension UIApplication: AppSwitcher {}

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n Xcode 16, I can no longer extend UIApplication to conform to my AppSwitcher protocol without encountering errors. It worked perfectly in Xcode 15.

Solution

  • This is a change in the iOS SDK. The open method now has more annotations on its completion handler - @MainActor and @Sendable.

    You should add those to your protocol method too.

    public protocol AppSwitcher {
    @MainActor
    func open(
        _ url: URL,
        options: [UIApplication.OpenExternalURLOptionsKey: Any],
        completionHandler completion: (@MainActor @Sendable (Bool) -> Void)?
    )
}

    Also consider using the async version of the open method in your protocol.

    public protocol AppSwitcher {
    @MainActor
    func open(_ url: URL, options: [UIApplication.OpenExternalURLOptionsKey : Any]) async -> Bool
}

    If this change breaks some other parts of your code, that means you were not using open in a concurrency-safe way in the first place.