kotlinlang #coroutines

Lets say i want to update a user location every 30 seconds, currently i use a runnable with a handler to make this work. Is there a better way to do this is kotlin? Thread in Slack Conversation

louiscad

11/25/2018, 2:11 PM

Hi all, do you think such a class should be in kotlinx.coroutines?

Copy code

import kotlinx.coroutines.CoroutineDispatcher
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.withContext

open class SuspendLazy<out T>(
    private val dispatcher: CoroutineDispatcher = Dispatchers.Default,
    initializer: () -> T
) {
    private val lazyValue = lazy(initializer)
    suspend operator fun invoke(): T = with(lazyValue) {
        if (isInitialized()) value else withContext(dispatcher) { value }
    }
}

Tolriq

11/25/2018, 2:59 PM

Opening a new thread as I'm lost as finding the cause 😞 Using https://gist.github.com/Tolriq/dcbdc62c0e29d3b321034e990c3c85ce I have some crashes that are properly handled that are thrown by coroutines somewhere. I'm using the correct workaround 1 from https://github.com/Kotlin/kotlinx.coroutines/issues/830 So I suppose there's another place causing coroutines to throw the original unwrapped exception, but I can't find where 😞 I've tried to add a CoroutineExceptionHandler to the scope and exceptions are still thrown 😞 My only remaining guess would be that https://gist.github.com/Tolriq/dcbdc62c0e29d3b321034e990c3c85ce#file-okhttpworkerpool-kt-L70 there's something to do with CompletableDeferred and cancellation but can't find anything about that.

Alexey Pushkarev

11/25/2018, 9:01 PM

Hi everyone! Could someone please explain me why I can't call one suspend function inside another ?

asad.awadia

11/26/2018, 2:33 AM

Is getting a key from redis considered a blocking call? Should it be wrapped in a

withContext

Paul Woitaschek

11/26/2018, 9:30 AM

I have this function where I'm counting down dates. Now line 5 is suspending. The compiler warns me that it can only be called from within a coroutine body

mersan

11/26/2018, 10:16 AM

any way to not let IntelliJ get stuck when you try to decompile the Kotlin bytecode when there are coroutines used in the code?

Sam

11/26/2018, 2:34 PM

Is there a way to iterate over coroutineContext?

Orfeo Ciano

11/26/2018, 3:26 PM

Quick one: do you have any github repo with examples, good patterns, antipatterns for structured concurrency on Android???

👍 3

asad.awadia

11/26/2018, 3:56 PM

If I use

suspendCoroutine

to wrap an async callback into a suspend function - which dispatcher does it use to run on? The same dispatcher that called it?

👍 1

Sam

11/26/2018, 7:58 PM

How do i create a class implementing a suspend block?

Copy code

class LambdaClass : suspend () -> Unit {

    override fun invoke() {
        // do something
    }

}

mersan

11/26/2018, 10:47 PM

I'll be giving a small introduction into coroutines at the work, any modifications or additions on this?

-.md

👍 2

asad.awadia

11/27/2018, 12:49 AM

How to

await

for completion of a suspending function that wraps a blocking call with

withContext

Andrew Gazelka

11/27/2018, 1:52 PM

My coroutine approach for calculating prime numbers is slower (by about 700ms... total = 6700ms) , even when grouping multiple prime calculations. Any idea why or how I can make this faster? https://gist.github.com/andrewgazelka/977ade9862f7fd6fff686b6bdc1db70c

oshai

11/27/2018, 2:00 PM

I am having an issue with 1.0.1:

java.lang.NoClassDefFoundError: kotlinx/coroutines/SupervisorJobImpl

Sam

11/27/2018, 10:49 PM

What am i missing here? handler is not invoked

Copy code

fun main( args : Array<String> ) {

    val handler = CoroutineExceptionHandler { _, throwable -> println( "Handled $throwable" ) }

    runBlocking(handler) {

        launch {
            println( "Handler is ${coroutineContext[CoroutineExceptionHandler]}" )
            delay( 1000)
            println( "first task" )
            throw UnsupportedOperationException()
        }

    }

}

spand

11/28/2018, 8:19 AM

If I use the pattern of using a

Job()

as an explicit lifecycle as mentioned here: https://github.com/Kotlin/kotlinx.coroutines/blob/master/docs/coroutine-context-and-dispatchers.md#cancellation-via-explicit-job Is installing a

CoroutineExceptionHandler

the only way to handle exceptions in the lifecycle ?

Tolriq

11/28/2018, 11:16 AM

Just a quick question about what is better and differences between GlobalScope and withContext(NonCancellable) on Android Is there any advantage / problem with one of those functions? Typical use case would be using proper scoped context in an Activity, but wanting that a coroutine that write something to the DB is not cancelled at the end of the activity. Or maybe there's another alternative?

Pavel.AZ

11/28/2018, 11:29 AM

Hey, since Actor and Channels are ObsoleteCoroutinesApi, what should we use instead?

bloder

11/28/2018, 12:19 PM

Hi, what's the best way to run many tasks in parallel at the same time and wait its results with coroutines?

Diefferson

11/28/2018, 1:12 PM

Hi, based on class Result I create class ResultAsync to encapsulate Coroutines results, what do you think about?

bdawg.io

11/29/2018, 6:47 AM

Is there a way to configure the maximum number of active concurrent coroutines in a CoroutineScope/Context?

Tolriq

11/29/2018, 9:05 AM

Is there a simple way to have a channel / workerpool that can only have 1 active coroutine? (Meaning that any message send while the coroutine is running would be dropped). From reading I understand that CONFLATED will have 1 in the queue + 1 running, and that RendezVous would suspend the send and not ignore it.

mingkangpan

11/29/2018, 11:08 AM

I have a question: if I am launching a coroutines, and want to return and cancel it, if some if condition doesn't fullfil how do I do? like this?

Copy code

launch {
   val isYes = channel.receive
   if(!isYes) {
       coroutineContext.cancel()
       return@launch
   }
   
   //process further logic
}

gotoOla

11/29/2018, 1:30 PM

Are there any known memory gotchas that were introduced with the 1.0 release and switch to structured concurrency (where launch and async are extensions on a coroutinescope?) The reason why I am asking is that we have had a service running for quite a long while with kotlin 1.2.61 and when we tried to bump it to kotlin 1.3 we are continously increasing in memory until we eventually crash

myanmarking

11/29/2018, 7:14 PM

i would assume in #1 the scope gets captured inside the foorLoop, which isnt the case

dewildte

11/30/2018, 5:06 AM

Anybody working with kotlin's actors?

☝️ 1

Joey Heck

11/30/2018, 8:03 PM

Copy code

val job = GlobalScope.launch {
    <How do I access the Job from here>
}

Tolriq

11/30/2018, 8:07 PM

What is the proper way to implement suspendCancellableCoroutine but for coroutine / suspend code?

Copy code

suspend fun doLoad() = suspendCancellableCoroutine<Result> {
        val cancellationSignal = CancellationSignal()
        it.invokeOnCancellation { cancellationSignal.cancel() }
        val result = query.cancellationSignal(cancellationSignal).executeAsync()
        if (cancellationSignal.isCanceled) {
            it.resume(Result.Cancelled)
        } else {
            it.resume(Result.Success(result))
        }
    }

In that example all works if executeAsync is blocking, but if executeAsync is a suspend function this no more works. Since cancellation rely on the cancellation signal how to merge the 2 worlds?

v79

12/01/2018, 8:12 AM

Suppose I have an arbitrary list of

suspend

functions p(), q(),..., and I want them to run in parallel/concurrently. Is this a valid approach?

-.kt