kotlinlang #coroutines

val progress = Channel<Long>(Channel.CONFLATED)
			val progressList = GlobalScope.async { progress.toList() }

			runBlocking {
				val progressResult = (0L..20L step 2).onEach { progress.offer(it) }
				progress.close()

				assertThat(progressResult.toList()).toBe(progressList.await())
			}

progressList

is []...

adibfara

10/22/2018, 11:16 AM

is there a way to override Dispatchers.UI on unit tests in android? it's trying to use Looper.getMainLooper() which is a stubbed method

Nikky

10/22/2018, 11:36 AM

compile("something>name:version") { exclude(name = "excludedDependency") }

louiscad

10/22/2018, 11:41 AM

@adibfara You can see how I did it for unit tests in the AndroidX Lifecycle integration PR in kotlinx.coroutines repo.

louiscad

10/22/2018, 12:41 PM

Yes @robin, you can do it this way:

coroutineScope {
    val daemonLikeJob = launch { while (true) /* Do sth until everything is done */ }
    coroutineScope {
        launch { /* do work */ }
        launch { /* do work */ }
    }
    daemonLikeJob.cancel()
}

myanmarking

10/22/2018, 1:49 PM

e: java.lang.IllegalStateException: failed to analyze: java.lang.ArrayIndexOutOfBoundsException
	at org.jetbrains.kotlin.analyzer.AnalysisResult.throwIfError(AnalysisResult.kt:56)
	at org.jetbrains.kotlin.cli.jvm.compiler.KotlinToJVMBytecodeCompiler.compileModules$cli(KotlinToJVMBytecodeCompiler.kt:125)
	at org.jetbrains.kotlin.cli.jvm.K2JVMCompiler.doExecute(K2JVMCompiler.kt:161)
	at org.jetbrains.kotlin.cli.jvm.K2JVMCompiler.doExecute(K2JVMCompiler.kt:57)
	at org.jetbrains.kotlin.cli.common.CLICompiler.execImpl(CLICompiler.java:96)
	at org.jetbrains.kotlin.cli.common.CLICompiler.execImpl(CLICompiler.java:52)
	at org.jetbrains.kotlin.cli.common.CLITool.exec(CLITool.kt:93)
	at org.jetbrains.kotlin.daemon.CompileServiceImpl$compile$1$1$2.invoke(CompileServiceImpl.kt:441)
	at org.jetbrains.kotlin.daemon.CompileServiceImpl$compile$1$1$2.invoke(CompileServiceImpl.kt:101)
	at org.jetbrains.kotlin.daemon.CompileServiceImpl$doCompile$$inlined$ifAlive$lambda$2.invoke(CompileServiceImpl.kt:1020)
	at org.jetbrains.kotlin.daemon.CompileServiceImpl$doCompile$$inlined$ifAlive$lambda$2.invoke(CompileServiceImpl.kt:101)
	at org.jetbrains.kotlin.daemon.common.DummyProfiler.withMeasure(PerfUtils.kt:137)
	at org.jetbrains.kotlin.daemon.CompileServiceImpl.checkedCompile(CompileServiceImpl.kt:1062)
	at org.jetbrains.kotlin.daemon.CompileServiceImpl.doCompile(CompileServiceImpl.kt:1019)
	at org.jetbrains.kotlin.daemon.CompileServiceImpl.compile(CompileServiceImpl.kt:440)
	at sun.reflect.GeneratedMethodAccessor106.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:346)
	at sun.rmi.transport.Transport$1.run(Transport.java:200)
	at sun.rmi.transport.Transport$1.run(Transport.java:197)
	at java.security.AccessController.doPrivileged(Native Method)
	at sun.rmi.transport.Transport.serviceCall(Transport.java:196)
	at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:568)
	at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:826)
	at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$0(TCPTransport.java:683)
	at java.security.AccessController.doPrivileged(Native Method)
	at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:682)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.ArrayIndexOutOfBoundsException

patjackson52

10/22/2018, 2:24 PM

Are there any libraries yet to support common operators on channels? I am referring to Rx-type operators. There is a good article here with several examples. Seems like these could be shared in a library/libraries ( https://github.com/Kotlin/kotlinx.coroutines/blob/master/reactive/coroutines-guide-reactive.md)

Schadenfreude

10/22/2018, 2:27 PM

Hey guys, any coroutine gurus around who can help me out with something?

enleur

10/22/2018, 8:33 PM

Looking for an advice on limiting concurrency. My problem is that I want to limit parallel running coroutines per some token(user, credentials, whatever) created on demand. Current implementation works, but not sure about it: https://gist.github.com/enleur/4bdd04b0e2c54b94f84a2ca62ca9b6ac

nwh

10/22/2018, 9:01 PM

Why isn't

withContext

an extension on

CoroutineScope

? Don't `launch`/`async` do more than just switch context?

elect

10/22/2018, 9:41 PM

trying to play with coroutines in 1.3 190 I get:

Class 'kotlinx.coroutines.BuildersKt__Builders_commonKt' is compiled by a pre-release version of Kotlin and cannot be loaded by this version of the compiler Class 'kotlinx.coroutines.CoroutineStart' is compiled by a pre-release version of Kotlin and cannot be loaded by this version of the compiler Class 'kotlinx.coroutines.Job' is compiled by a pre-release version of Kotlin and cannot be loaded by this version of the compiler Class 'kotlinx.coroutines.Job' is compiled by a pre-release version of Kotlin and cannot be loaded by this version of the compiler

spierce7

10/22/2018, 10:10 PM

In the RC it appears that

newSingleThreadContext()

has been removed. What should I be using instead?

spierce7

10/22/2018, 10:51 PM

Is there a better way to create a

CoroutineContext

than this? I used to be able to do

CoroutineContext(Dispatcher)

, but that doesn't seem to work anymore.

spierce7

10/23/2018, 3:14 AM

I see there is a private API to create a context that reuses threads from the Default dispatcher, but limits it's parallelism to a single thread, i.e.

LimitingDispatcher

. Is this supported in a public API yet?

Schadenfreude

10/23/2018, 10:00 AM

Hey guys, I’m trying to write a simple coroutine to await a callback and return a value, but for some reason my code hangs and the response never comes. Here’s the gist: https://gist.github.com/Schadenfeude/8d0ccb88eb1b874d4e3cbf43327fe266 The last log I see is the one on line 19

Log.d("BillingManagerProvider", "suspendCoroutine: startConnection")

deviant

10/23/2018, 3:56 PM

I've updated to

1.0.0-RC1

and now all my actors and channels marked as

obsoleted api

. What apis should we use instead?

rocketraman

10/23/2018, 5:12 PM

I have a database DAO from which I want to return a

Sequence

. However, I also want to close the db cursor when the sequence has finished consuming. Is this a valid approach?

suspend fun findSomethings(...): Sequence<Something> {
  val cursor = ...
  return sequence {
    cursor.use {
      yieldAll(cursor.iterator())
    }
  }
}

spierce7

10/23/2018, 7:25 PM

I'm seeing some issues with the given proguard file for latest version kotlinx.coroutines for Android. Any idea where I can find a proper pro-guard definition?

gildor

10/24/2018, 3:26 AM

We started migration of our Android apps to Structured Concurrency implementation from kotlionx.coroutines (before we used own solution for that) and now I have question about CoroutineScope. Looks that for any UI component SupervisorJob is the best choice (it’s even mentioned on Coroutines guide, see https://github.com/Kotlin/kotlinx.coroutines/blob/master/docs/exception-handling.md#supervision), because you usually don’t want to cancel all the jobs is one of them failed on your UI component, this is especially important for

async

builder, because you handle result only when call

await

and don’t want to cancel all other coroutines and especially CoroutineScope of this UI component if one of our async jobs is failed, we can actually handle error when call await() And you need non-supervisor Job and scope only in case if you want to run a few operations in parallel and want to cancel them if one of them failed, but it’s specific and explicit case, at least in usual UI development So I have 2 points here: 1. Should coroutine guide recommend to use SupervisorJob for all UI components and not Job (what is now standard in documentation, for example check

CoroutineScope

docs which use Job in Android Activity). Otherwise it can cause a lot of very subtle bugs when you use CoroutineScope for UI development. 2. We need some easy way to start non-supervisor scope. Now the only way to do that is

CoroutineScope(coroutineContext + Job())

which is quite wordy way. maybe make sense to change

coroutineScope

default implementation and create new Job instance if outer context contains SupervisorJob If it make sense for someone, I would happy to create an issue and contribute, but maybe I missed some important use cases there

sdeleuze

10/24/2018, 10:32 AM

@elizarov Watching

https://www.youtube.com/watch?v=nKJbDYRsO0s▾

, I am wondering if in long term future (let say Java 17 LTS since there is now a release each 6 months) it would make sense to think about Coroutines that would run on fibers (1 coroutine = 1 fiber) on the JVM to improve monitoring, debuggability, maybe performances. Any thoughts?

fabianterhorst

10/24/2018, 10:47 AM

which repository url do i have to include to use coroutines version 1.0.0-rc1? Im not able to resolve it with

maven { url "<https://dl.bintray.com/kotlin/kotlinx/>" }

0.30.2-eap13 works just fine.

kirillrakhman

10/24/2018, 1:42 PM

@elizarov and everybody here: Do you think there is value in educating devs about the difference between - async as in OS-level async IO and - async as in doing a blocking call on a thread pool ? Both approaches unblock the calling (main) thread but I think the scaling characteristics are way different. Maybe it's not that important on a client but on the server you should be able to get way more concurrency using true OS-level asynchronicity which requires the proper libraries.

👍 4

lukaswelte

10/24/2018, 1:47 PM

When using a DB connection pool like HikariCP. Should one opt for

<http://Dispatchers.IO|Dispatchers.IO>

or a

newFixedThreadPoolContext

with the number of threads being the max DB pool size?

Jaroslav

10/24/2018, 2:20 PM

I’m trying to make something similar to what is done in kotlinconf app - https://github.com/JetBrains/kotlinconf-app/blob/master/konfios/konfswift/ui/UI.swift but the problem is, there is no such class

Kotlinx_coroutines_core_nativeCoroutineDispatcher

in my ios framework. I’m using 1.0.0-RC1 coroutines. Maybe it changed the name or something?

louiscad

10/24/2018, 2:22 PM

Before structured concurrency, such code would run properly:

launch {
    val someWorkAsync = async {
        throw CustomException()
    }
    delay(100)
    try {
        someWorkAsync.await()
    } catch (e: CustomException) {
        println("Handled it! $e")
    }
}

If I understood correctly, now, the whole scope is cancelled, even though the exception is handled properly when calling

await()

. How can I get the previous behavior? Create a

Job

that has scope's job as parent, and use it for

async(…) { … }

dave08

10/24/2018, 5:06 PM

Iterable.asReceiveChannel()

was deprecated (in 0.30.2) contrary to the other channel operators that were just marked obsolete. Any reason why? Even Rx has such adapters, and this could come in handy in Unit testing for mocking...

bolot

10/24/2018, 9:36 PM

Has anybody run into an issue

kotlin.Result cannot be cast to MyType

? I'm trying to use

Result

with LiveData, doing something like this:

liveData.value = runCatching { useCase().await() }

, which is then used in

liveData.observe

result.onSuccess { } .onFailure { }

(Kotlin version 1.3.0-rc-190)

Title

bolot

10/24/2018, 9:36 PM

Has anybody run into an issue

kotlin.Result cannot be cast to MyType

? I'm trying to use

Result

with LiveData, doing something like this:

liveData.value = runCatching { useCase().await() }

, which is then used in

liveData.observe

result.onSuccess { } .onFailure { }

(Kotlin version 1.3.0-rc-190)

gildor

10/24/2018, 11:15 PM

Maybe this issue https://youtrack.jetbrains.com/issue/KT-27105

There are still some known issues with Result

Or that https://youtrack.jetbrains.com/issue/KT-27586

bolot

10/24/2018, 11:21 PM

Thank you!

Exactly the same issue. I'll use my own, non-inline Result class for now. Thanks again!

amatkivskiy

11/25/2018, 10:02 AM

Seems that this is more related to inline classes issue rather then to specific Result class.

💯 1

View count: 5