Hello, I'm starting to explore KMM and I have a ba...

# multiplatform

[Daniele Andreoli]

Hello, I'm starting to explore KMM and I have a basic question that I didn't notice in official doc: how to actually consume coroutine / suspend function in ios module? And especially in a ViewController? Thanks.

[Tom Wayne]

Hello there. In my company we consume all return values from KMM code as flows. So we basically dont call suspend function from iOS code at all.

[Tom Wayne]

This is how we wrap the Flow, to be easily consumed in iOS code:

class CommonFlow<T>(private val origin: Flow<T>) : Flow<T> by origin {

    fun watch(block: (T) -> Unit): Closeable {
        val job = Job()

        onEach {
            block(it)
        }.launchIn(CoroutineScope(job + Dispatchers.Main))

        return object : Closeable {
            override fun close() {
                job.cancel()
            }
        }
    }
}

[Tom Wayne]

Maybe somebody will give you better answer 🙂

[John O'Reilly]

Recommend taking a look at https://github.com/rickclephas/KMP-NativeCoroutines

[Daniele Andreoli]

Thank you both. 🙂 Very nice answers

[John O'Reilly]

fwiw wrote short post recently about using that library.....in this case using new Swift 5.5 concurrency approach (but library also supports Combine and RxSwift as well) https://johnoreilly.dev/posts/kmp-native-coroutines/

[Osman Saral]

I don't know where I saw it but we use almost the same as @Tom Wayne

expect class CommonFlow<T>(origin: Flow<T>): Flow<T>

fun <T> Flow<T>.asCommonFlow(): CommonFlow<T> = CommonFlow(this)

//Android
actual class CommonFlow<T> actual constructor(origin: Flow<T>): Flow<T> by origin

//iOS
actual class CommonFlow<T> actual constructor(origin: Flow<T>): Flow<T> by origin {
    val scope = MainScope(Dispatchers.Main)

    fun observe(block: (T) -> Unit): Closeable {
        onEach { block(it) }.launchIn(scope)

        return object : Closeable {
            override fun close() {
                scope.cancel()
            }
        }
    }
}

I will also add how we close the returned closeable from Swift side, so someone can tell me if I did something wrong 😅 . I'm not sure if I'm creating a retain cycle here :

public typealias Disposal = [Disposable]

extension Ktor_ioCloseable {
    func add(to disposal: inout Disposal) {
        let disposable = Disposable(self)
        
        disposal.append(disposable)
    }
}

public final class Disposable  {
    private let closable: Ktor_ioCloseable

    init(_ closable: Ktor_ioCloseable) {
        self.closable = closable
    }

    deinit {
        print(":::deinit is calling")
        closable.close()
    }

    public func add(to disposal: inout Disposal) {
        disposal.append(self)
    }
} 

//on the call site
private var disposal = Disposal()

myFlow.observe { state in
            ///...
}.add(to: &disposal)

[Bolu Okunaiya]

@Osman Saral I have the same thing implemented and i've been looking to see if retain cycles get created but none so far

[Osman Saral]

Great thanks @Bolu Okunaiya