Hi folks I m using `newSingleThreadExecutor` as a Dispatcher kotlinlang #coroutines

# coroutines

05/01/2020, 9:50 PM

Hi folks, I'm using

newSingleThreadExecutor

as a Dispatcher but I have a problem with it, when I use

delay(x)

, other functions that use the same dispatcher does not execute until the delay finish. Why this is happening if

delay

does not block the Thread.

octylFractal

05/01/2020, 9:56 PM

can't reproduce, can you show code?

fun main() {
    val dispatcher = Executors.newSingleThreadExecutor().asCoroutineDispatcher()
    runBlocking(dispatcher) {
        launch {
            println("Foo!")
            delay(1000L)
            println("After Foo!")
        }
        launch {
            println("Bar!")
            delay(1000L)
            println("After Bar!")
        }
    }
}

Foo!
Bar!
After Foo!
After Bar!

05/01/2020, 9:59 PM

I fix it. The problem was that I have something like this:

withContext(singleThread) {
   coroutineScope.launch(singleThread) {
      delay(x)
   }
}

When I migrate it to a function thar produce a Job, fix the problem, But why ?

05/01/2020, 10:01 PM

withContext

suspends until all the coroutines launched in its scope complete.

05/01/2020, 10:27 PM

Good to know that, tkx Roman.

05/02/2020, 5:27 PM

Just for may understanding:

coroutineScope {}

also does that, right? So it is only

async

launch

that fire off jobs that are executed in parallel, while a scope ending of

coroutineScope

withContext

suspends until every child coroutine is completed.

octylFractal

05/02/2020, 5:29 PM

yes, that's correct -- though it is incorrect to say only

async

launch

start parallel jobs, other things like

produce

actor

Flow.launchIn

can also do so -- many methods that take a coroutine scope and aren't suspend will start a separate job

05/02/2020, 8:57 PM

Thanks a lot!