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#coroutines
Title
# coroutines
d

detouched

10/13/2017, 5:09 AM
Hi there, may I have a hopefully quick review please? I'm trying to implement a version of
select
that waits for the first successful result (opposed to the existing one that waits for the first completed clause, no matter exceptionally or not). First of all, am I reinventing the wheel? If not, here's what I ended up with – does it make sense? Any issues you can see here?
Copy code
private suspend fun <R, D : Deferred<R>> selectFirstSuccessful(deferredList: List<D>,
                                                               failedDeferredList: List<D>): Triple<R?, List<D>, List<D>> =
        if (deferredList.isEmpty()) {
            Triple(null, deferredList, failedDeferredList)
        } else {
            try {
                select<Triple<R?, List<D>, List<D>>> {
                    deferredList.forEach { deferred ->
                        deferred.onAwait { result -> Triple(result, deferredList - deferred, failedDeferredList) }
                    }
                }
            } catch (e: Exception) {
                val completedExceptionally = deferredList.filter { it.isCompletedExceptionally }
                val notCompletedExceptionally = deferredList - completedExceptionally
                selectFirstSuccessful(notCompletedExceptionally, completedExceptionally + failedDeferredList)
            }
        }
Full code with usage example is here: https://gist.github.com/detouched/73f366cb730ece629b9141dea96d3a98
v

voddan

10/13/2017, 6:03 PM
Sounds like a useful facility for the standard library
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