Is it possible to set multiple CompletionHandler on a job kotlinlang #coroutines

02/15/2019, 10:00 PM

Is it possible to set multiple CompletionHandler on a job?

zak.taccardi

02/15/2019, 10:12 PM

IIRC correctly, use. for these kinds of questions, it’s useful to write a quick unit test to confirm

just register multiple completion handlers that output some logs on a scope, and run it

02/15/2019, 10:13 PM

Oh yeah, i did try, i don't see API support

public fun invokeOnCompletion(handler: CompletionHandler): DisposableHandle

seems like the next request overwrites the previous one

02/15/2019, 10:19 PM

@Sam “seems” as in you’re registering two handlers in code and the first one isn’t getting called when you execute the code?

02/15/2019, 10:20 PM

in my case, i'm using a helper method from a library

library is setting a CompletionHandler for its own cleanup

so i'm wondering how i can set one? I guess, i will have to ask the API to provide another callback

kind of chained implementation

02/15/2019, 10:26 PM

I’m not sure what your test code is, but I wrote one real quick:

suspend fun main() = coroutineScope<Unit> {
    val job = launch { delay(1000) }

    job.invokeOnCompletion { println("handler one called") }
    job.invokeOnCompletion { println("handler two called") }
    job.invokeOnCompletion { println("handler three called") }
}

handler one called
handler two called
handler three called

02/15/2019, 10:30 PM

Thanks, this does work

I'm not sure why my callback fails

02/15/2019, 10:31 PM

If your callback throws an exception:

Installed [handler] should not throw any exceptions. If it does, they will get caught, wrapped into [CompletionHandlerException], and rethrown, potentially causing crash of unrelated code.

02/15/2019, 10:32 PM

Hmmm, okay, will check the library implementation

Thanks for the tip