kotlinlang #coroutines

atm we wrap the callback code in some code which uses CompletableFutures and then use coroutines await() .. which is some overhead we actually don't need

marstran

04/05/2018, 12:08 PM

You can do that with the

suspendCoroutine

function. Check this: https://github.com/Kotlin/kotlin-coroutines/blob/master/kotlin-coroutines-informal.md#wrapping-callbacks

bitkid

04/05/2018, 12:10 PM

exactly what i was looking for. thx a lot @marstran!

Joey Heck

04/05/2018, 6:42 PM

I posted this in general, but was advised to use this channel 🙂 (incoming messages)

groostav

04/05/2018, 6:42 PM

Hey guys, I've mentioned this before but I want to bring it up one more time because I'm clearly thinking differently than many; I want a

SequentialExecutorFacade

, which takes an executor as "backing executor", and simply ensures that all calls to

submit

execute

schedule (if scheduled)

, etc, all run jobs seemingly on a single thread. I dont need gaurentees about which thread its run on but I want gaurentees that only 1 job will be run at a time.

groostav

04/05/2018, 6:43 PM

I made a stunningly poor implementation of this concept which is now biting me in the butt, and I'm wondering if i apache/google/kotlinx commons either had a solution or if i could emplore them to offer one.

groostav

04/05/2018, 6:44 PM

I guess, putting it another way, I want an

ExecutorService

that gives me the same behaviour as the code put in an

actor {

block --albeit that code gets this behaviour through `Channel`s semantics rather than intrinsically

venkat

04/06/2018, 1:17 AM

Since Kotlin already has: -

producers

(think: sources), -

actors

(=sinks) and -

Channels

(=edges), Throw in: -

transforms

and -

pipes

for easy hookup we end up with DAGs
, not unlike NodeJS’ streams. Here’s an early proof of concept: https://github.com/venkatperi/kotlin-coroutines-lib/blob/master/src/main/kotlin/com/vperi/kotlinx/coroutines/experimental/TransformChannel.kt

Copy code

runBlocking {
      FS.createReader(inputFile.toPath())
        .pipe(decodeUtf8())
        .pipe(splitLines())
        .pipe(spy({ println("> $it") }))
        .pipe(contents({
          assertEquals(lines.size, it.size)
        }))
    }

where:

Copy code

// doesn't handle lines split across buffers
fun splitLines() = transform<String, String> {
  var count = 0
  input.consumeEach {
    it.split("\n").forEach {
      output.send("${count++}: $it")
    }
  }
}

More in the tests…

albertgao

04/06/2018, 2:23 AM

Android app:

onClick

is a clickHandler for a button I try to get a result from a http get call. But it only prints

, not even prints

. Not to mention the result. Simply just not there. get function has been tested. It works. What am I missing here?

-.groovy

user

04/06/2018, 2:41 AM

@gildor commented on @albertgao’s file https://kotlinlang.slack.com/files/U822EMCSH/FA23YBH2P/-.groovy: As general comment I would recommend do not use HttpUrlConnection with coroutines but use async client for that, for example okhttp.

-.groovy

user

04/06/2018, 2:45 AM

@gildor commented on @albertgao’s file https://kotlinlang.slack.com/files/U822EMCSH/FA23YBH2P/-.groovy: Also

bg

function is not good choice for IO.

bg

uses own fixed thread pool (

2 * availableProcessors()

), so it make some sense, but usually for network you need more flexible thread strategy and also no sense to limit number of threads by CPU for IO

-.groovy

user

04/06/2018, 3:13 AM

@albertgao commented on @albertgao’s file https://kotlinlang.slack.com/files/U822EMCSH/FA23YBH2P/-.groovy: Believe me Andrey, I won’t use this API if I have a choice. 😞 For the 2nd topic, any doc i can learn from?

-.groovy

user

04/06/2018, 3:20 AM

@gildor commented on @albertgao’s file https://kotlinlang.slack.com/files/U822EMCSH/FA23YBH2P/-.groovy: At least you can write proper async abstraction over it using coroutines. Learn about what? What is better threading strategy for networking? Or about

bg

? Just check source code of bg, it’s just a wrapper function over async with predefined coroutine dispatcher

-.groovy

user

04/06/2018, 3:23 AM

@albertgao commented on @albertgao’s file https://kotlinlang.slack.com/files/U822EMCSH/FA23YBH2P/-.groovy: How could I forget about the source code…. Thanks. I believe this is a good start! 🙂

-.groovy

user

04/06/2018, 3:23 AM

@gildor commented on @albertgao’s file https://kotlinlang.slack.com/files/U822EMCSH/FA23YBH2P/-.groovy: https://github.com/Kotlin/anko/blob/master/anko/library/generated/coroutines/src/bg.kt

-.groovy

Kulwinder Singh

04/06/2018, 12:15 PM

i have created this function to run a code block after given time. this is working fine ,but i don't know much about

coroutines

so is this code is ok .also i have read that

async

will create new

coroutine

each time so does it destroy

coroutine

after work is finished or it will remain in memory ?

is_it_Right__.kt

🚫 1

user

04/06/2018, 12:19 PM

@altavir commented on @Kulwinder Singh’s file https://kotlinlang.slack.com/files/U5FHN1J7L/FA38UJC9L/is_it_right__.kt: Why not use

delay

method? instead of ugly contraption?

is_it_Right__.kt

altavir

04/06/2018, 12:20 PM

https://github.com/Kotlin/kotlinx.coroutines/blob/master/coroutines-guide.md#waiting-for-a-job

user

04/06/2018, 12:30 PM

@Kulwinder Singh commented on @Kulwinder Singh’s file https://kotlinlang.slack.com/files/U5FHN1J7L/FA38UJC9L/is_it_right__.kt: what is wrong in my code (i know my code is not correct but i want to know what is wrong in it?,because i have created some more functions similar to this) ?

is_it_Right__.kt

altavir

04/06/2018, 12:42 PM

I don't say it is incorrect. I did say that there is a very good method in standard library to handle this situation. Please read the documentation (I've provided the link).

user

04/06/2018, 12:46 PM

@Kulwinder Singh commented on @Kulwinder Singh’s file https://kotlinlang.slack.com/files/U5FHN1J7L/FA38UJC9L/is_it_right__.kt:

Copy code

fun doAfter(seconds: Long, work: () -> Unit) {
    launch(UI) {
        delay(seconds)
        work.invoke()
    }
}

i have also changed funtions , so is it right now ?

is_it_Right__.kt

altavir

04/06/2018, 12:47 PM

Seems to me that way, but you have to test it yourself.

altavir

04/06/2018, 12:48 PM

Though delay uses milliseconds, not seconds

altavir

04/06/2018, 12:49 PM

In tour code there is also not need for coroutines since

work

is not suspended.