Coroutines Interop

[Intektor]

I was wondering why you use your own State implementation instead of using MutableStateFlow. Is there any benefit in using your State implementation, as it looks like it's just an observer pattern? As I really like to use flows, I was also asking myself if there is something similar to the Android viewModelScope, a componentScope maybe, that is cancelled when the component is killed.

[arkivanov]

Hello and thanks for the question.

I was wondering why you use your own State implementation instead of using MutableStateFlow

This is required to avoid direct dependency on kotlinx.coroutines. One may prefer another library (e.g. Reaktive or RxJava). Or if Jetpack Compose is used as UI framework, then there is State and you may not need coroutines as well.

Another benefit of using Value is better interoperability with Swift. Value is a normal class with normal functions and callbacks - it can be easily exposed to Swift and subscribed/unsubscribed there.

Also please note, that Value is directly used only in Router. Usually its state is exposed to UI and subscribed without coroutines - e.g. val routerState = root.routerState.subscribeAsState(). For anything else you a free to use whatever you like.

I was also asking myself if there is something similar to the Android viewModelScope, a componentScope maybe, that is cancelled when the component is killed

Since components are lifecycle-aware, you are free to create your own coroutine scope!

fun LifecycleOwner.coroutineScope(context: CoroutineContext): CoroutineScope {
    val scope = CoroutineScope(context)
    lifecycle.doOnDestroy(scope::cancel)

    return scope
}

And then use it in a component as follows:

class SomeComponent(componentContext: ComponentContext): ComponentContext by componentContext {
    private val scope = coroutineScope(Dispatchers.Main)
}

[Burtan]

While you can get to the idea to do this yourself, you might add this to the documentation as it is mandatory when using coroutines.

[arkivanov]

Sure thing! Filed #150.

[arkivanov]

Updated the docs - https://arkivanov.github.io/Decompose/component/scopes/

[arkivanov]

Value should be also beneficial when exporting Decompose components to JavaScript (binaries.library()).