Hi everyone, first of all thanks for the great eff...

# decompose

[sigmadelta]

Hi everyone, first of all thanks for the great effort and time invested in the Decompose library as I’m already enjoying the benefits it provides.

Second, I’m currently using it in a Compose-Desktop application, and I’m in a situation where I need to launch a few coroutines but I’m a little bit confused as to how the main & io `CoroutineContext`s are defined. On the documentation page (https://arkivanov.github.io/Decompose/component/scopes/#creating-a-coroutinescope-in-a-component) I found following sample:

fun CoroutineScope(context: CoroutineContext, lifecycle: Lifecycle): CoroutineScope {
    val scope = CoroutineScope(context)
    lifecycle.doOnDestroy(scope::cancel)
    return scope
}

fun LifecycleOwner.coroutineScope(context: CoroutineContext): CoroutineScope =
    CoroutineScope(context, lifecycle)

class SomeComponent(
    componentContext: ComponentContext,
    mainContext: CoroutineContext,
    private val ioContext: CoroutineContext,
) : ComponentContext by componentContext {

    // The scope is automatically cancelled when the component is destroyed
    private val scope = coroutineScope(mainContext + SupervisorJob())

    fun foo() {
        scope.launch {
            val result =
                withContext(ioContext) {
                    "Result" // Result from background thread
                }

            println(result) // Handle the result on main thread
        }
    }
}

In the SomeComponent constructor you are passing mainContext and ioContext . Do these need to be defined in the RootComponent or just the parent component? And aside from that, how exactly are they instantiated?

Thanks again

[Arkadii Ivanov]

There are multiple options. You can pass Dispatchers.Main.immediate or <http://Disaptchers.IO|Disaptchers.IO> (or any other dispatcher) directly when calling the function. Or you can also pass dispatchers via component constructors. You can also do the following - SomeComponent(ioContext: CoroutineContext = <http://Dispatchers.IO|Dispatchers.IO>). You can substitude a dispatcher with TestDispatcher in unit tests.

[Andrew Steinmetz]

Another trick you can do is make your own custom component context and provide the dispatchers through that. I did that once in this kmm app which helped reduce some boiler plate of always passing dispatchers in through the constructor directly. Then you can create a test component context that provides the test dispatchers.