If i create a coroutineScope inside a flow which launches In viewModelScope. Will the `coroutineScop...

# coroutines

[Ravin Jain]

If i create a coroutineScope inside a flow which launches In viewModelScope. Will the coroutineScope gets cancelled when the Job created from viewmodelscope.launch is cancelled ?

[Ravin Jain]

init {
    a = viewModelScope.launch {
        abc()
    }
}

fun abc() = flow<Boolean> {
    val b = coroutineScope {
        // some operations
        emit(true)
    }
}

override fun onCleared() {
    super.onCleared()
    a.cancel()
}

When I do a.cancel will b be cancelled automatically ?

[ephemient]

1. flow() is not designed for that, use channelFlow() instead

[ephemient]

the way you've constructed it here, the scope inside flow is unrelated to viewModelScope, so no

[Ravin Jain]

Is it safe to pass the viewmodelscope inside function as parameter and then use that

[ephemient]

if you want to change context inside the flow builder, use channelFlow

[ephemient]

maybe take a moment to check, what are you trying to achieve?

[Ravin Jain]

So my basic use case is that I want the viewmodelScope inside the flow {}

[ephemient]

the (cold) flow builder should get dispatched on whatever it's collected on, but it doesn't have direct access to that scope

[Ravin Jain]

What if I use the channelFlow and start a new coroutine using launch inside channelFlow and then use the coroutineScope
Will the coroutine scope inside launch will be same as the flow's coroutineScope (viewmodelScope)

[ephemient]

it'll be a direct child of the viewmodelscope (not the same exact scope as it's a different job)
but note that channelFlow closes when its builder returns, which launch() doesn't block

[Ravin Jain]

hmmm you are right
What about the producerScope

[gildor]

What are you trying to achieve? It’s not clear from your code, for example abc flow is never collected
Also why do you need coroutineScope inside of flow?

[K Merle]

You could write abc().last() and make flow run only once as a suspend function.

[K Merle]

And .last() will cancel if viewModelScope gets canceled. You could create custom CoroutineScope and inject it into your ViewModel and use it. This way you'll be able to send that event when your ViewModel onCleared gets called.