(also returns the object that matched)

Something is definitely funky with doing it my way because the second time I press my button (which triggers the vMS.launch{}, I get two Log statement prints inside of the if (status == "SUCCESS"), but the first time I land here I only get one log statement. So far though my code above "works", it just doesn't seem "right"

This is what I currently have. It "works"

fun confirmEvent(successEvent: () -> Unit) {
  viewModelScope.launch {
    var response = repository.getIdFromServer()

    if (response.isValid) {
      var response2 = repository.getObjectWithCurrentStatus(response.data.id)

      //Keep listening to changes on the server until the status changes from IN_PROGRESS TO SUCCESS
      response2.collect {
        if (it.status != "IN_PROGRESS") {
          if (it.status == "SUCCESS") {
            successEvent()
          } else {
            state.errorDialog = true
            state.errorDialogText = "Error 2: " + it.status
          }
        }
      }
    } else {
      state.errorDialog = true
      state.errorDialogText = response.errorText
    }
  }
}

Switching over to

first

does not work. But maybe I did it wrong?

fun confirmEvent(successEvent: () -> Unit) {
  viewModelScope.launch {
    var response = repository.getIdFromServer()

    if (response.isValid) {
      var response2 = repository.getObjectWithCurrentStatus(response.data.id)

      //Keep listening to changes on the server until the status changes from IN_PROGRESS TO SUCCESS
      val waiting = response2.first {(it.status == "SUCCESS")}
      
        if (waiting.status != "IN_PROGRESS") {
          if (waiting.status == "SUCCESS") {
            successEvent()
          } else {
            state.errorDialog = true
            state.errorDialogText = "Error 2: " + waiting.status
          }
        }
      }
    } else {
      state.errorDialog = true
      state.errorDialogText = response.errorText
    }
  }
}

@Adam Powell Actually wait. it seems to work now? I swear the first time I launched it it didn't work. I swear I just freakin hit this issue in AS again. https://issuetracker.google.com/issues/191997469 Lol. Anyway. Im going to run some more tests, but yes first{} seemed to have done exactly what I was expecting it to do. One last thing though (and i guess maybe its not worth the hypothetical question), but how would I do this if

first

didn't exist and

collect

is all I had?

Would i go the route that I said before of cancelling/stopping the coroutine scope?

I wonder if this would just be the right approach

viewModelScope.launch {

        beaconService.streamTest().collect {

            //Do something then
            this.coroutineContext.job.cancel()

        }
}

I read also that is customary for functions that launch a coroutine and return immediately to be defined as extensions on coroutine scope

Right

But the first operator is the right way for your scenario

tl;dr: throw

who knew this would get so confusing. Interestingly enough

this.coroutineContext.job.cancel()

did seem to work also.

Sucks that

throw

isn't mentioned at all here. https://stackoverflow.com/questions/57088428/kotlin-flow-how-to-unsubscribe-stop

if you consider what flows are and how they work, throw is the only thing that can do what you want here. Consider a flow that iterates over a collection:

flow {
  for (item in list) {
    emit(item)
  }
}

how can something called by

emit

cause that

for

loop to stop iterating other than by throwing?

or add in resource management:

flow {
  val thing = openThing()
  try {
    while (thing.hasMore()) {
      emit(thing.readMore())
    }
  } finally {
    thing.close()
  }
}

how do you make this code stop reading this resource before it's finished and properly clean up?

sort of a side rant but this sort of thing is why it makes me sad when people get religion about returning result types to the exclusion of throwing exceptions at all. There are good reasons to dislike APIs that use exceptions inappropriately but what they do is incredibly useful when you need to say, "I could not meet the contract of what you asked me to do" up layers of the call stack

thank you adam! cheers

And if you need to terminate the flow early, but

first { ... }

isn't enough,

takeWhile { ... }

or

transformWhile { ... }

may be useful so you don't need to deal with the exceptions yourself.