Let me offer this conceptual model:

launch

is just like starting a new thread. If the code inside

launch

crashes with exception then it is considered “uncaught” exception and, generally, should crash your app (on Android that happens automatically). However, when you use

async

and the execution results with exception, then this exception gets stored inside the

Deferred

. It is your obligation to process it later. So: -

launch

- fire and forget, crash application on uncaught error; -

async

- launch and

await

for result later. You must

await

on a coroutine that you’ve created with

async

. You MUST NOT forget about the coroutine you’ve started with async.

or we can catch exception in

invokeOnCompletion()

after

launch

is finished. or it's not recommended?

You cannot “catch” it with invokeOnCompletion. You can only get notified on it.

do you have some examples? din't find it in the doc

No samples. That is all we have now: https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.experimental/-coroutine-exception-handler/index.html

so we use it like

launch(UI+myExHandler)

?

yes

thanks! i'll try it

Added that to stackoverflow: https://stackoverflow.com/questions/46226518/what-is-the-difference-between-launch-join-and-async-await-in-kotlin-coroutines/46226519#46226519