Hello, I have a pretty basic question about iOS in a KMP project. Say I have an interface defined in...

# multiplatform

[zsperske]

Hello, I have a pretty basic question about iOS in a KMP project. Say I have an interface defined in my common code that looks like this.

interface Database {
     suspend fun updateEntry(foo: Foo) : Boolean
}

In order to implement this on iOS one option appears to be implementing a kotlin class in my iosMain that could use obj-c interop to achieve what I want. Is it also possible to feed a swift class that I've written (with obj-c headers) into my common code? Are there drawbacks to that?

[basher]

you can feed a Swift class to Kotlin. Obj-C headers aren't needed. Swift compiler will let you know that to implement the interface, which is exported as an Obj-C protocol, you'll need to make your Swift class inherit from NSObject

[Kris Wong]

in Kotlin 1.4 this will create a callback based binding for you

[Kris Wong]

in 1.3 you can add one yourself

[zsperske]

Thank you both for the replies, do you know of any examples of this on github or in the docs?

[zsperske]

After some more searching, I found this post: https://discuss.kotlinlang.org/t/kotlin-native-suspendable-functions-inside-ios-framework/8132

[zsperske]

It seems I'm running into the same issue as this guy, the protocol being generated for me is empty. I'm gonna check out the suggestions that he was given though

[Kris Wong]

suspend functions are removed in 1.3

[basher]

oh i missed the suspend bit of this. for this on iOS, we make a callback-based fun, which is compatible in 1.3. then we make an internal suspend extension that calls the callback version using this https://github.com/autodesk/coroutineworker#waiting-on-asynchronous-callback-based-work

[zsperske]

Cool! Thanks again

[zsperske]

am I going down the right path here?

override suspend fun addEvent(host: User, event: Event): Boolean {
        return suspendCoroutine {
            addEvent(it)
        }
    }

    open fun addEvent(callback: Continuation<Boolean>) {
        throw NotImplementedError("iOS project should implement this")
    }