Would it be correct to say that this code: `withContext(<http://Dispatchers.IO|Dispatchers.IO>) { ...

# coroutines

[CLOVIS]

Would it be correct to say that this code:

withContext(<http://Dispatchers.IO|Dispatchers.IO>) {
  foo()
}

is conceptually equivalent as this one:

launch(<http://Dispatchers.IO|Dispatchers.IO>) {
  foo()
}.join()

Since the implementation is very different, I expect that for performance reasons it does something else, but as a developer should I use withContext as syntax sugar for launch().join(), or is there something else I need to know about?

[louiscad]

@CLOVIS if the second one crashes, it will cancel the parent scope, and have the Throwable propagate up the scopes until caught, while the former will just throw from its call site.

[CLOVIS]

Really good to know, thanks!

[Stylianos Gakis]

Would the top one not also cancel the parent scope? If not, why not? That must also have started at some point with launch() { // } as well. I don't really understand the exact differences there.

[louiscad]

@Stylianos Gakis If the top one is surrounded with a try catch block, it'll not crash the scope, while for the second one, the scope will crash (cancelling any other childs, the siblings of the crashed coroutines) and propagate the exception anyway.

[Stylianos Gakis]

Aha, so even if the bottom option is also surrounded with try catch on the call site, it will still crash since it's inside a different job (? or what would that be called?) it will crash and propagate up. Thanks for the clarification!

[louiscad]

The second option launches a child job. By crash, I mean throwing something other than a CancellationException that is uncaught in that launch { … } call.