does collecting two flows inside the same coroutineScope influence each other when the coroutine con...

# coroutines

[Remy Benza]

does collecting two flows inside the same coroutineScope influence each other when the coroutine context is a SupervisorJob?

[Remy Benza]

example:

val scope = CoroutineScope(SupervisorJob() + Dispatchers.Main)

scope.launch {

flow1.collect { //code }

flow2.collect { //code }

}

[Remy Benza]

if the collection of flow1 fails? does flow2 run normally? I think I would because of the SupervisorJob context. But I've experience flow2 does not get collected.

[Natsuki(开元米粉实力代购)]

there's nothing to do with SupervisorJob , that's becoz in semantic flow is cold, thus when runs flows2.collect that indicate flow1.collect is done, use launchIn or fire another launch with each collect

[KamilH]

collect is a suspend function so it suspends until flow1 finishes. It’s always better to use onEach + launchIn combination

[Remy Benza]

can you provide a snippet how would you do this

[KamilH]

flow1.onEach { 
    // handle new value here
}.launchIn(scope)

scope.launch { 
    flow1.collect { 
        // handle new value here
    }
}

[KamilH]

These two are doing the same - lets you launch new coroutine and collect items

[KamilH]

The difference is that you can do this:

flow1.onEach {

}.launchIn(viewModelScope)

flow2.onEach {

}.launchIn(viewModelScope)

without waiting for flow1 to finish, while here:

viewModelScope.launch {
    flow1.collect {

    }
    flow2.collect {

    }
}

flow2.collect will be called only after flow1 finished

[Remy Benza]

thnx, and does the fact you're using a `Job`or `SupervisorJob`for the context play a role in the outcome?

[KamilH]

In this context no. If I’m not mistaken it would make a difference only when one of them (collections) throw an exception. In Job case whole job would be cancelled while in SupervisorJob it wouldn’t

[dewildte]

Here you have two flows in a single coroutine.
If there is an uncaught exception thrown then the coroutine it is in will be canceled and then the scope the coroutine is in will also be canceled. If the scope has a SupervisorJob then the scope will not be canceled.

[dewildte]

As for the collection of the two flows influencing the other, the answer is yes if they are collected in the same coroutine.

[dewildte]

.collect does not start a new coroutine, it just suspends the current coroutine until the collection is complete.

[Remy Benza]

thnx for your explanation