rememberCoroutineScope

rememberCoroutineScope for Event-Triggered Work

An onClick lambda cannot call a composable such as LaunchedEffect. For work the user starts, rememberCoroutineScope() returns a scope that is cancelled when its call site leaves:

EffectDemos.kt: a snackbar launched from a clickKotlin

    Button(onClick = {
      scope.launch {                             // started by an event, not by composition
        Log.d(FX, "snackbar: show")
        try {
          val result = snackbar.showSnackbar("Added to cart", actionLabel = "Undo")
          Log.d(FX, "snackbar: $result")
        } catch (e: CancellationException) { Log.d(FX, "snackbar: cancelled"); throw e }
      }
    }) { Text("Add to cart") }

Add to cart, five seconds, Undo; then Add to cart and Close panel, which removes the panel:

Output of 92

D/BookNestFx: snackbar: show
D/BookNestFx: snackbar: ActionPerformed
D/BookNestFx: snackbar: show
D/BookNestFx: snackbar: cancelled

With an action label the snackbar waits indefinitely; closing the panel cancelled it. Work that must outlive the screen belongs in viewModelScope (ViewModel and UDF).

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