:wave: hey folks Has anyone tried to expose an interface with a suspend function and implementing t...

# ios

[Nikolay Kasyanov]

👋 hey folks

Has anyone tried to expose an interface with a suspend function and implementing this interface in Swift? Is it even expected to work?

I’m trying this rn and if I call completionHandler not on the same thread the “coroutine” method was called on, I get illegal sharing exception:

class DependencyImpl: FooBarDependency {
    func getName(completionHandler: @escaping (String?, Error?) -> Void) {
        ...
    }
}

When thread stays the same, it’s all good. I’m using coroutines 1.5.1-native-mt.

Kotlin code in comments.

[Nikolay Kasyanov]

I’m guessing coroutine continuations cannot be shared, hence the exception?

[Nikolay Kasyanov]

class FooBar(val dependency: Dependency) {
    interface Dependency {
        suspend fun getName(): String
    }

    fun doStuff(callback: (String) -> Unit): Disposable {
        val suspendCall: suspend () -> String = dependency::getName

        return suspendCall
            .asSingle()
            .subscribeOn(ioScheduler)
            .observeOn(mainScheduler)
            .map { "Hello $it" }
            .subscribe {
                callback(it)
            }
    }
}

[Nikolay Kasyanov]

looking at the way coroutine -> Reaktive bridging is implemented, looks very similar to https://youtrack.jetbrains.com/issue/KTOR-1073

https://github.com/badoo/Reaktive/blob/mt-coroutines/coroutines-interop/src/commonMain/kotlin/com/badoo/reaktive/coroutinesinterop/LaunchCoroutine.kt

[russhwolf]

The built-in suspend function translation is expected to only work single-threaded (and maybe only main-threaded, I don't remember for sure). It's limited by the fact that it exists at the language level and so can't make use of constructs from the kotlinx.coroutines library. Might be interesting to see what happens in the new memory model preview though. I haven't looked at that yet.

[Nikolay Kasyanov]

Thanks for chiming in @russhwolf, sticking to single thread for now.

[Alexander Ignatiev]

hi
I had a similar problem
it helped me

DispatchQueue.main.async {
    completionHandler()
}