协程的父子关系，获取特定的孩子并取消？

Question

I've this following suspend function

override suspend fun getStories(type: Int) {
    val job: Job = coroutineScope { 
        launch { 
            delay(20000)
        }
        
        launch {
            delay(50000)
        }
    }
}

As per my understanding a coroutine Job can have children, which in this case will be the two launch coroutines. My question is fairly simple. How can I cancel the delay(50000) coroutine?

I did run an iterator on job.children() method, but it was not fruitful. Next I checked if a job has a get method for it's children. ♂️

Lemme know if it's not possible, or what's the point of children if I can't access them to individually call cancel?

Answer 1

Actually job.children does work. Maybe the problem is how, where or when you're calling it. This code works for me:

fun main() = runBlocking {
    val job: Job = launch {
        launch {
            println("First job started")
            delay(3000)
            println("First job finished")
        }.invokeOnCompletion {
            println("First job completed!")
        }

        launch {
            println("Second job started")
            delay(4000)
            println("Second job finished")
        }.invokeOnCompletion {
            println("Second job completed!")
        }

        launch {
            println("Third job started")
            delay(5000)
            println("Third job finished")
        }.invokeOnCompletion {
            println("Third job completed!")
        }
    }

    delay(1000)
    job.children.elementAt(2).cancel()
    delay(750)
    job.children.elementAt(0).cancel()
    delay(500)
    job.children.elementAt(0).cancel()
}

This is the output:

First job started
Second job started
Third job started
Third job completed!
First job completed!
Second job completed!