Hi, I am a bit confused about Kotlin Coroutines Jobs. Is it the case that a job can only run once? I wanted to launch the

searchJob

every time my search parameter changed in the example below. What happens is that the

searchJob

is called successfully the first time I pass my parameter, but never again after that. Could someone please have a look ?

How are you using the

searchJob

variable outside of this?

No, that's the only place.

So you define a variable somewhere named

searchJob

and only assign it here? You might want to launch the coroutine with an Coroutine exception handler passed into it to see if there is a hidden exception cancelling the coroutine

Yes, I define it and use it in the viewModel:

private var searchJob: Job? = null

I have been using a tutorial and adapting it to my own project... I'll do what you suggest. So does it mean that the searchJob needs to be cancelled properly in order to be reused?

I don't believe you can reuse job references, once it reaches its final state of cancelled or completed it is done. But the job reference shouldn't have any impact here as long as you aren't manually cancelling it somewhere else. Does the "search job started" not print a second time or is the contents inside of the flow not working?

The "search job started" does not print a second time.

That's really odd, you may want to override onCleared in the view model and see if the view model scope itself is getting cancelled. Because it looks like it should run a second time from my brief glance

Ok, thanks for your help. I will check it out.

what is `getFeeds`' return type? Is it flow? If yes, do you apply a terminal operator (e.g. collect) on it? I mean snippet you shared includes only onEach which is not terminal, and alone will have no effect

Yes, it's a flow. this is the whole snippet:

fun onSearch(searchTitle: String) {
        _searchTitle.value = searchTitle
        println("on search started")
        searchJob = viewModelScope.launch {
            delay(1000L)
            println("search job started")
            getFeeds(searchTitle)
                .onEach { result ->
                    when (result) {
                        is Resource.Success -> {
                            _isRefreshing.value = false
                            _state.value = state.value.copy(
                                newsFeedItems = result.data ?: emptyList(),
                                isLoading = false,
                                isSuccess = true,
                                isError = false
                            )
                            println("is success")
                        }

                        is Resource.Error -> {
                            _isRefreshing.value = false
                            _state.value = state.value.copy(
                                newsFeedItems = result.data ?: emptyList(),
                                isLoading = false,
                                isSuccess = false,
                                isError = true
                            )
                        }

                        is Resource.Loading -> {
                            _isRefreshing.value = true
                            _state.value = state.value.copy(
                                newsFeedItems = result.data ?: emptyList(),
                                isLoading = true,
                                isSuccess = false,
                                isError = false
                            )
                        }
                    }
                }.launchIn(this)
        }
    }

is

viewModelScope

normal androidx' scope? If no (e.g. if it's manually created), that might happen if you have an unhandled exception somewhere. You can change

println("on search started")

to

println("on search started ${viewModelScope.coroutineContext.job.isActive}")

to check if VM is somehow cancelled second time

Yes it's

androidx.lifecycle.viewModelScope

The result of

println("on search started ${viewModelScope.coroutineContext.job.isActive}")

is "True" the first time and "False" the second time.

Yes, GlobalScope is not recommended, since the jobs created using that scope might outlive your fragment/activity. I didn't work with Hilt, so can't help there but better to find who causes viewModelScope to cancel

Oh right, thanks, I deleted these questions because I thought they were not relevant.