What is the purpose of `join` now that the outer scope will wait for all functions launched within t...

# coroutines

[SUPERCILEX]

What is the purpose of join now that the outer scope will wait for all functions launched within to complete?

[elizarov]

Sometime you need to join your particular children before doing something else:

[elizarov]

val subTask = launch { doSomething() } 
// do something else in parallel
subTask.join()
// continue only when subTask completes
// do more stuff

[elizarov]

that is fork-join type of programming style (launch == fork)

[SUPERCILEX]

I thought of that too

[SUPERCILEX]

But then why not just use withContext at that point?

[elizarov]

A what point?

[elizarov]

you can also use coroutineContext to the same effect:

coroutineContext { 
    launch { doSomething() } 
    // do something else in parallel
}
// continue only when subTask completes
// do more stuff

But that is more nesting in code

[SUPERCILEX]

Interesting

[SUPERCILEX]

Nevermind about with context, o got myself confused

[SUPERCILEX]

I guess what bothers me about your code sample is that has two different indentations for parallel work which makes things unclear

[SUPERCILEX]

Wouldn't this be better code?

[SUPERCILEX]

val subTask = async { doSomething() }
val sub2 = async { ... }

awaitAll(subTask, sub2)

// do more stuff

[SUPERCILEX]

Or is the point that the first launch just needs to do some background with and we don't care about a result?

[elizarov]

Yes. You use launch if you need side-effect of some work (like store stuff to DB). You use async if you need result of some work.

[SUPERCILEX]

Ahhhhh, finally putting it all together. Thanks so much!!! ❤️

[SUPERCILEX]

And I've been using coroutines for a year, lol