in `suspendCancellableCoroutine { continuation -&g...

# coroutines

[Tuan Kiet]

in suspendCancellableCoroutine { continuation -> do we need to check anything like isActive or isCancelled before call resumeWith and why?

[Dominaezzz]

No not really.

[Dominaezzz]

All you have to do is register a hook. continuation.invokeOnCancellation or something like that.

[voben]

I think you do, otherwise your synchronous code will continue to run even though the coroutine might have been cancelled. I think its a good idea to perform the check before calling resume

[voben]

Say you’re working with Google play api, and you want to use the addOnCompleteListener callback with coroutines, so you decide to wrap this in a suspendCancellableCoroutine to get the power of coroutines with your callback.

If the coroutine gets cancelled, the code in the addOnCompleteListener could still be running. Which means once your addOnCompleteListener callback finishes, before calling resume on the suspended function, its probably a good idea to check if that coroutine has been cancelled

return suspendCancellableCoroutine { cont ->
        addOnCompleteListener {
            val e = exception
            if (e == null) {
                @Suppress("UNCHECKED_CAST")
                if (isCanceled) cont.cancel() else cont.resume(result as T)
            } else {
                cont.resumeWithException(e)
            }
        }
    }

Example source
https://github.com/Kotlin/kotlinx.coroutines/blob/master/integration/kotlinx-coroutines-play-services/src/Tasks.kt