iOS: Concurrency is only available in iOS 15.0.0 or newer in protocol

Question

I have an app which deployment target is iOS 12.1, with many protocols defining functions with completion handlers, i.e.

protocol P {
    func f(_ completion: @escaping: (String) -> Void)
}

I would like to replace all these with the new async/await iOS 15 syntax, for a better code readability:

protocol P {
    func f() async -> String
}

But when doing so, I get the error:

Concurrency is only available in iOS 15.0.0 or newer

What is a good solution for this, considering that I just cannot switch the deployment target from 12.1 to 15.0?

Thank you for your help

Answer 1

The short answer is "there is currently no solution." If you want your apps to run on iOS 12 and earlier, you can't use the async/await calls, unless you want to write 2 versions of all your async code, one that runs on iOS < 15, and the other that runs on iOS ≥ 15.

As George mentions in his comment, Apple is trying to figure out how to "back-depoloy" async/await support. If they are able to do that, you will be able to use the modern approach with older versions, but I would bet Apple will not go back as far as iOS 12.

Edit:

See Bradley's comment below. The best you will get is async/await support in iOS 13, if Apple is able to pull that off. From the link Bradley posted, iOS 12 definitely won't be supported.

Answer 2

For other people who are looking facing this issue on 15.0 target. This is likely related to your XCode version, you need to be have minimum XCode 13.2 or later to compile code which uses Swift Concurrency on versions older than iOS 15.