calling launch within launch is not structured concurrency a

Question

calling launch within launch is not structured concurrency anymore right ```val upperJob = launch val jobFoo1 = launch foo1 val jobFoo2 = launch foo2 upperJob cancel won t cancel jobFoo1 and jobFoo2``` right I have to use `async` here

Kirill Prybylsky · Answer

what behaviour you want to achieve

mingkangpan · Answer

I want to load 2 sets of data from 2 differnt APIs if one fails the other should not be cancled but I still want to be able to cancel both at once

Kirill Prybylsky · Answer

easy use like this

Kirill Prybylsky · Answer

but exception from first or second will be propagated up so you have to handle it

mingkangpan · Answer

how where to put try catch and whats the difference here to async

Kirill Prybylsky · Answer

Use try catch for the most upper coroutine or coroutineExceptionHandler Difference between async launch you can get in docs

mingkangpan · Answer

okay launch and async will both excute the calls parallel

Kirill Prybylsky · Answer

yep

mingkangpan · Answer

```launch try supervisorScope first api launch second api launch cathc e Exception ``` ```launch try supervisorScope first api async second api async cathc e Exception ```

mingkangpan · Answer

basically both will do what I want

Kirill Prybylsky · Answer

but with async you have to call await to get the result

mingkangpan · Answer

are you android developer

Kirill Prybylsky · Answer

android app developer

mingkangpan · Answer

```override fun onChanged t AccountInfo fetchDataAfterAccountInfo cancel fetchDataAfterAccountInfo = viewModelScope launch try supervisorScope launch val purchases = appService fetchPurchasesWithPickupData purchases pickPurchasesLiveData postValue purchases launch val paymentPlan = appService fetchPaymentPlan paymentPlanLiveData postValue paymentPlan instalments catch e Exception Timber e e loading data after accountInfo failed ```

mingkangpan · Answer

so basically that s what I want to to do after a new accountInfo I load 2 sets of data which are independent from each other but I want to be able to cancel both if there is a new accountInfo what do you think

Kirill Prybylsky · Answer

Here is complete code snippet

mingkangpan · Answer

if first api fails what s the resultOfAll 0 then

Kirill Prybylsky · Answer

well yes move resultOfAll inside supervisor scope

Kirill Prybylsky · Answer

or like this

mingkangpan · Answer

if first api fails will second api executes uninfluenced

Kirill Prybylsky · Answer

yes second will not be cancelled

mingkangpan · Answer

lets maybe go back to my android code snippet where should I put `liveData posValue`

Kirill Prybylsky · Answer

let me check

Kirill Prybylsky · Answer

code snippet that you sent is great so you can use it wink

mingkangpan · Answer

so if both apis fails for example I will get two exception means timber will log 2 times exploding head

Kirill Prybylsky · Answer

yep no exceptions will be lost

mingkangpan · Answer

okay if it is really like this then this is for sure too magical

mingkangpan · Answer

exploding head

Kirill Prybylsky · Answer

lol

mingkangpan · Answer

< Kirill Prybylsky>

mingkangpan · Answer

need to disappoint

mingkangpan · Answer

``` fun main = runBlocking try supervisorScope launch foo1 launch foo2 delay 1000 println Waited 1000ms catch e Exception println e suspend fun foo1 delay 300 throw RuntimeException Something went wrong suspend fun foo2 Int delay 500 println returning 5 return 5 ```

mingkangpan · Answer

```Exception in thread main java lang RuntimeException Something went wrong at com minki example MainKt foo1 Main kt 20 at com minki example MainKt$foo1$1 invokeSuspend Main kt at kotlin coroutines jvm internal BaseContinuationImpl resumeWith ContinuationImpl kt 33 at kotlinx coroutines DispatchedTaskKt resume DispatchedTask kt 173 at kotlinx coroutines DispatchedTaskKt dispatch DispatchedTask kt 111 at kotlinx coroutines CancellableContinuationImpl dispatchResume CancellableContinuationImpl kt 305 at kotlinx coroutines CancellableContinuationImpl resumeImpl CancellableContinuationImpl kt 315 at kotlinx coroutines CancellableContinuationImpl resumeUndispatched CancellableContinuationImpl kt 397 at kotlinx coroutines EventLoopImplBase$DelayedResumeTask run EventLoop common kt 484 at kotlinx coroutines EventLoopImplBase processNextEvent EventLoop common kt 271 at kotlinx coroutines BlockingCoroutine joinBlocking Builders kt 79 at kotlinx coroutines BuildersKt BuildersKt runBlocking Builders kt 54 at kotlinx coroutines BuildersKt runBlocking Unknown Source at kotlinx coroutines BuildersKt BuildersKt runBlocking$default Builders kt 36 at kotlinx coroutines BuildersKt runBlocking$default Unknown Source at com minki example MainKt main Main kt 5 at com minki example MainKt main Main kt returning 5 Waited 1000ms```

mingkangpan · Answer

uncaught exception is thrown so launch is a differnce to async

Kirill Prybylsky · Answer

expected behaviour of coroutines put try catch block inside of supervisorScope i think we missed something

mingkangpan · Answer

still the same launch and async have difference exception propagation

streetsofboston · Answer

< mingkangpan> Maybe this can help you a bit Exceptional Exceptions for Coroutines made easy by Anton Spaans