kotlinlang #coroutines

I have a boolean property that is changed based on the state of a Service (in Android) to which I want to receive updates from an Activity (everything on the UI thread). Should I use

ConflatedBroadcastChannel<Boolean>

for that, or is this overkill and should I use something else?

Sorin

04/06/2018, 7:51 PM

Good question. I also would like to use channels as an event bus for the communication between service and an activity. The only thing I could think of was Singleton Receiver channel. I am very new to coroutines. What would be a solution?

bj0

04/06/2018, 9:22 PM

there are lightweight eventbus libraries available that take care of a lot of the details for you, unless your case is very simple it would probably be easier to just use one

Sorin

04/07/2018, 12:22 PM

@bj0 thx for your answer. The thing is I want to avoid extra dependencies only for that use case. I used an RxBus basically a singleton PublishSubscriber before and before that Otto and EventBus. But now, I want to move away from rxJava2 and reduce even more the dependencies so I want to do as much as I can on top of coroutines.

Sorin

04/07/2018, 12:23 PM

Meanwhile I found a solution that seems to work.

Sorin

04/07/2018, 12:23 PM

Copy code

/**
 * You can use like this.
 * val channel = EventBus().asChannel<ItemChangeAction>()
 * launch (UI){
 *   for(action in channel){
 *     // You can use item
 *     action.item
 *   }
 * }
 */
@Singleton
class EventBus @Inject constructor() {
    val bus: BroadcastChannel<Any> = ConflatedBroadcastChannel()

    fun send(o: Any) {
        launch {
            bus.send(o)
        }
    }

    inline fun <reified T> asChannel(): ReceiveChannel<T> {
        return bus.openSubscription().filter { it is T }.map { it as T }
    }
}

Sorin

04/07/2018, 12:23 PM

@louiscad might satisfy your use case.

groostav

04/09/2018, 9:42 AM

I'm writing a file system listener in kotlin with coroutines, anyone care to review my code?

File_watching_implementation.kt

user

04/09/2018, 12:26 PM

@kingsley commented on @groostav’s file https://kotlinlang.slack.com/files/U0ZFBBUBU/FA3C0A8CS/File_watching_implementation.kt: Hey @groostav This is really cool. While I’m trying not to think so much about the file watcher API itself, I have a few comments that would be interesting to take a look at: I was thinking it might be nice to take advantage of channel’s map/flatMap operators to transform these producers, since this is basically what is happening AFAICS. What do you think? Also, instead of explicitly specifying

worker

for all those subsequent channels, I’d use

coroutineContext

, since they were all launched within the

worker

anyway Finally, I’d replace the

while(true)

with

while(isActive)

File_watching_implementation.kt

groostav

04/09/2018, 10:15 PM

I actually had

map

and

filter

in mind when writing these but I couldn't find them, so i simply went with for-each loops. are these operators defined somewhere in

kotlinx.coroutines

already? your right, but my

LiveThreadFactory.create()

stuff just adds to debugability, since it will wrap the ForkJoinPool (aka CommonPool on java7+) in some thread-renaming stuff. I played with the idea of aiming for something like

launch(CommonPool + Renaming)

, but order-of-operations became an issue, and it also made for what I thought were odd lifecycles, so I just kept what is something of a convention already for me. and

while(true)

while(isActive)

is an OK idea, but watchService actually throws something similar to

ChannelIsClosedException

when you call

watchService.close()

, so I've actually updated the above code to include a

try { while(true) send(take()) } catch(ex: CannotTakeException) { log.fine("watch service closed", ex) }

pakoito

04/09/2018, 10:30 PM

I actually had
map
and
filter
in mind when writing these but I couldn’t find them, so i simply went with for-each loops. are these operators defined somewhere in
kotlinx.coroutines
already?

https://github.com/arrow-kt/arrow/blob/master/modules/effects/arrow-effects-kotlinx-coroutines/src/main/kotlin/arrow/effects/DeferredK.kt

pakoito

04/09/2018, 10:30 PM

😛

groostav

04/10/2018, 3:09 AM

I've actually got a copy of funktional 0.8 floating around on my classpath, maybe ill use this to finally get over to arrow

pakoito

04/10/2018, 10:24 AM

upon checking again, we’re not wrapping those

pakoito

04/10/2018, 10:24 AM

only deferred

Paul Woitaschek

04/10/2018, 3:25 PM

Is it possible to mark junit tests suspending? (currently I wrap all my tests in another runBlocking).

johannes.lagos

04/11/2018, 11:35 AM

I have a coroutine in a presenter that when the api throws a throwable it try to post to ui. The coroutine it wrapped by try & catch and launch(UI).

johannes.lagos

04/11/2018, 11:36 AM

However, still getting CalledFromWrongThreadException

johannes.lagos

04/11/2018, 11:37 AM

I have other coroutine with same pattern and those works fine even when throw an exception

johannes.lagos

04/11/2018, 11:39 AM

This is my code

-.kt

gildor

04/13/2018, 9:16 AM

doFirstStuff will be always called before doSecondStuff, but both tasks itself will run in parallel

gildor

04/13/2018, 9:18 AM

or even replace

async

with

launch

if you don’t want to do something after those tasks (so you don’t care about await())

louiscad

04/13/2018, 9:45 AM

suspend operator fun invoke()

on a

companion object

is so neat!

❓ 1

K 3

otakusenpai

04/14/2018, 6:05 PM

So, i think i hav a data race or something....

-.txt

otakusenpai

04/14/2018, 6:07 PM

In main.kt, the var m1 gets created and then it calls its function asyncParse() which calls the Parse function... and then prints the contents of its member msg which is of type MsgData through retMsgData()