(RxJava3) If you're creating an observable to emit...

# compose

[Dan Peluso]

(RxJava3) If you're creating an observable to emit values and subscribing in your composable with subscribeAsState() , is there a way to unsubscribe from that? Code in thread

[Dan Peluso]

I know you can create a disposable and get rid of that, but as far as I know you cannot use the subscribeAsState() function with a disposable. I'm creating my observable with

private var obsVal =
    Observable.interval(20, TimeUnit.MILLISECONDS).subscribeOn(<http://Schedulers.io|Schedulers.io>()).share()

and would like to be able to reset it, but I'm unsure how to unsub with compose's function

[Leland Richardson [G]]

it will get unsubscribed with the subscribeAsState() call is no longer in the composition. For instance, in the code:

if (condition) { val x = y.subscribeAsState() }

The subscription would be removed when condition turned false

[Leland Richardson [G]]

it’s hard to tell without seeing more of your code, but you might find key useful here

[Leland Richardson [G]]

val value by key(index) { getSOmeObservable(index).subscribaAsState() }

[Leland Richardson [G]]

in this case, whenever index changes, the code inside of it will be a “new” part of the composition, and the previous one will get removed, and thus, unsubscribed

[Leland Richardson [G]]

not sure if that makes sense. if not, shoot over some more of the code you’re wanting to write and i might be able to be more helpful

[Dan Peluso]

Is there any documentation for key? I can send over some code too

[Dan Peluso]

@Composable
fun renderGraph(plotType: PlotType) {
    // state
    val state = obsVal.subscribeAsState(initial = 0).value
    var plotState: PlotType by remember(calculation = { mutableStateOf(PlotType.PLOT0) })
    AndroidView(
        factory = {
            // create the chart
            // set the correct chart type when first building
            plotState = plotType
        },
        modifier = Modifier.fillMaxSize(),
        update = {
            // how the view knows to reset the graph
            if (plotType != plotState) {
                // update the chart data from $state
                // update the flag    
                plotState = plotType
                //TODO: reset the observable to emit values from 0 again
            }
        }
}

[Dan Peluso]

I'm calling this in a main view using the following

[Dan Peluso]

@Composable
fun MainView() {
    // state
    var tabPosition by remember(calculation = { mutableStateOf(0) })
    Column {
        TabRow(selectedTabIndex = tabPosition, tabs = {
            tabs.forEach { plotType ->
                Tab(selected = plotType.value == tabPosition, onClick = {
                    tabPosition = plotType.value
                },
                    text = { Text("Graph: ${plotType.value}") })
            }
        })
        renderGraph(PlotType.fromInt(tabPosition)!!)
    }
}