Hi, I need an advice. I would like to call suspend...

# compose

[Hyun]

Hi, I need an advice.
I would like to call suspend function on TextButton.onClick.
as onClick is not Composable.
I can’t use launchInComposition

so, I tried the below. but I’m not sure if this is proper approach or not.
I searched on this channel but. it was difficult to find the discussion.

scope = remember { CoroutineScope(SupervisorJob() + Dispatchers.Main.immediate) }
onDispose { scope.cancel() }

TextButton(onClick={ scope.launch { doSuspendFunction() }})

what is the best approach on this case?

[Leland Richardson [G]]

good question.

We might want to provide an API like this but we don’t yet.

Haven’t tested anything or tried this out. but something close to this might be a good interim solution. Ideally we provide something that allows you to use the corountinescope that launchInComposition uses which will work a little bit better but for the most part I think this would work okay:

class ComposableCoroutineScopeImpl(
    val context: CoroutineContext
) : CoroutineScope, CompositionLifecycleObserver {
    val job = Job()
    override val coroutineContext: CoroutineContext
        get() = Dispatchers.Default + job
    override fun onEnter() {}
    override fun onLeave() { job.cancel() }
}

@Composable
fun composableCoroutineScope(
    context: CoroutineContext = EmptyCoroutineContext
): CoroutineScope = remember {
    ComposableCoroutineScopeImpl(context)
}

[Hyun]

@Leland Richardson [G]
I’m really appreciated for the answer.🙏🙏🙏
I’ll do below with your code.

scope = composableCoroutineScope()

TextButton(onClick={ scope.launch { doSuspendFunction() }})

[Zach Klippenstein (he/him) [MOD]]

Are the contracts for onDispose and CompositionLifecycleListener.onLeave different? I thought the former would not get called if the composition failed before committing, and if that's true for the latter as well that means this code could leak the job/coroutine.

https://kotlinlang.slack.com/archives/CJLTWPH7S/p1591660760450000?thread_ts=1591653158.447300&cid=CJLTWPH7S

[Leland Richardson [G]]

hmm. tbh i didn’t think too carefully when i wrote this code. It’s possible if the composition got cancelled that it would have the wrong semantics, but if it got canceled then the onClick handler would never have a chance to get fired so i’m not sure this is an issue?

[Leland Richardson [G]]

you shouldn’t call scope.launch in the composition, only in an event handler or something like the original question had