So I know coroutine cancellation is cooperative, but I have a fairly simple case here that I'm not sure how to dig myself out of. I essentially have a button that calls

fetchMoreData()

fun fetchMoreData(i) {
  viewModelScope.launch { ...

but now if I call fetchMoreData() again, I actually want to cancel the old data fetching. How would I do that?

that answer is a bad idea; that job is not parented to the viewModelScope

Save the Job returned from the

launch

and cancel it before launching.

right, that's an option:

var fetchJob: Job? = null
fun fetch() {
    fetchJob?.cancel()
    fetchJob = viewModelScope.launch { ... }

Nice. I was hoping for something easy peasy... but I didn't know if this kinda felt like an rx-ism and so far everything ive ever brought from rx to coroutines has been wrong. hence I wanted to check.

you could also a flow as a trigger, e.g.

val fetchRequests = MutableSharedFlow<Unit>()
fun start() {
    fetchRequests.mapLatest { ... }.launchIn(viewModelScope)
}
fun fetch() {
    fetchRequests.tryEmit(Unit)
}

@ephemient for the sake of curiousotity. "right, that's an option:" whats some other options that come to mind. To me another option (which goes against the whole cancelling thing) would just be to treat it as a flow/queue and just finish off the current task, and then handle the next.

Note that it's a convention for a function that launches a coroutine and returns immediately to be an extension on CoroutineScope.

ooooh. i will read up on this. TIL