```fun main() = runBlocking { test() } suspend fun test() { val job = coroutineScope { ...

# coroutines

[Darren Gu]

fun main() = runBlocking {
    test()
}

suspend fun test() {
    val job = coroutineScope {
        launch {
            delay(5000)
        }
    }
    println("job = $job")
}

I need to have a reference to the job when it’s running. But the print doesn’t seem to execute until 5 sec later. What would be the correct way to achieve this?

[fatih]

It's because you are launching a new Coroutine. If you would have written print just after delay then since they are in the same Coroutine context they will be executed synchronously

[fatih]

Ohh didn't realize you are trying to print job. Sorry what do you really want to do with job? You want to wait job for to finish and do something?

[Darren Gu]

I need to start some other tasks in this suspend function. But I also need to get a reference to the job so I can cancel it later

[Darren Gu]

The thing is it has a be in a suspend function.

[Darren Gu]

is it even doable?

[fatih]

You can cancel the job as long as you have a reference to it

[Darren Gu]

Yes. but I won’t have the job until the coroutineScope returns. It won’t return until the job is finished

[Tijl]

coroutineScope

suspends until all child jobs finish, this explains your delay.

inside coroutineScope you have this

[Darren Gu]

so there is no way in a suspend function to start a new coroutine and let it run while I get the job reference?

[Tijl]

you say “new coroutine” but what you mean I guess is CoroutineScope? inside coroutineScope this refers to the scope which also consists of the Job AFAIK

[octylFractal]

you should do:

coroutineScope {
  val job = launch { delay(5000) }
 println("job = $job")
}

[Tijl]

that would be a more typical usage, yes

[Tijl]

but coroutineScope { this.coroutineContext } also contains a job AFAIK

[Darren Gu]

coroutineScope {} starts a new coroutineScope based on the current one that launched suspend function, correct?

[octylFractal]

based on the current suspend context, which is similar but not the same

[octylFractal]

all suspend functions have a coroutineContext available inside them

[Darren Gu]

Let’s say we do Coroutine(coroutineContext) in a suspend function. is it the same as coroutineScope {}

[octylFractal]

I presume you mean CoroutineScope(coroutineContext) -- no, coroutineScope also opens a new job, and if the current coroutineContext has a Job , the new one is a child of it

[Darren Gu]

what do you mean by a child of it. the doc says ” The provided scope inherits its coroutineContext from the outer scope, but overrides the context’s Job.”

[Darren Gu]

I am new to coroutine. I am sorry if I ask too many quesitons.

[octylFractal]

you may want to read https://kotlinlang.org/docs/reference/coroutines/basics.html#structured-concurrency

[Darren Gu]

I will read it again. Thank you very much!