CODEWITHSUNDEEP
exceptionkotlin-coroutines
lannyf
lannyf

Reputation: 11035

why having try/catch in corutineAScope block still crash by the exception caught

  fun main() = runBlocking {
        coroutineScope {

            val child = async {
                Log.e("+++", "+++  in  async{}, throw exception , ${Thread.currentThread().name}")
                throw Exception("test exception with await() in async")
            }

            try {
                child.await()
            } catch(ex: Throwable) {
                Log.e("+++", "+++  child.await() caught  exception $ex, ${Thread.currentThread().name}")
            }

        }
  }

The log "+++ child.await() caught exception java.lang.Exception: test exception with await() in aync, main" . shows the exception is caught, but it still crashes the app.

Why the expiation caught is still crashing the app with coroutines?

Upvotes: 0

Views: 683

Answers (3)

Gulzar Bhat
Gulzar Bhat

Reputation: 1337

Exception thrown by the child coroutine bubbles up to its immediate parent. You must try catching exceptions in parent coroutines. This way application won't crash.

Upvotes: 0

lannyf
lannyf

Reputation: 11035

find this is helpful as well, and here:

whenever a coroutine created by async() throws an exception, 
the same exception is thrown both by its Deferred.await() 
and inside the body of the parent coroutine as well! 
This means that, no matter if we catch the exception by surrounding await() with try/catch, 
our app is still going to crash because the exception is not thrown just 
from the await() suspension point

Upvotes: 1

Kiskae
Kiskae

Reputation: 25603

As per the documentation of coroutineScope:

This function is designed for parallel decomposition of work. When any child coroutine in this scope fails, this scope fails and all the rest of the children are cancelled (for a different behavior see supervisorScope). This function returns as soon as the given block and all its children coroutines are completed.

Remove the coroutineScope and it should function as you are expecting it should.

Upvotes: 1

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