Instant Search + Paging 3 + Flow

[GautierLouis]

Describe the bug 🐛
I'm implementing Instant Search on my android app using Paging 3 and flow to update the UI
I followed this article : https://www.algolia.com/doc/api-reference/widgets/multi-hits/android/#examples
This is quite simple but, for some reason either flow or live data are not updated when a query is typed.

To Reproduce 🔍
My entire ViewModel ->
```
private val searcher = MultiSearcher(
applicationID = ApplicationID("-----"),
apiKey = APIKey("----")
)
private val pagingConfig = PagingConfig(pageSize = 50)
private val indexProblem = IndexName(INDEX_PROBLEM)
private val indexArea = IndexName(INDEX_AREA)
private val problemSearcher = searcher.addHitsSearcher(indexName = indexProblem)
private val areaSearcher = searcher.addHitsSearcher(indexName = indexArea)
private val filterState = FilterState()
private val connection = ConnectionHandler()
private val problemPaginator = Paginator(
problemSearcher,
pagingConfig,
transformer = { hit -> hit.deserialize(ProblemRemote.serializer()) }
)
private val areaPaginator = Paginator(
areaSearcher,
pagingConfig,
transformer = { hit -> hit.deserialize(AreaRemote.serializer()) }
)

init {
    connection += filterState.connectPaginator(problemPaginator)
    connection += filterState.connectPaginator(areaPaginator)
}

val problems
    get() = problemPaginator.flow

val areas
    get() = areaPaginator.flow

fun search(query: String? = "") {
    searcher.setQuery(query)
    searcher.searchAsync()
}

override fun onCleared() {
    super.onCleared()
    searcher.cancel()
    connection.disconnect()
}

}

And in the onCreate of an activity

    searchViewModel.problems.onEach {
        println("RESULT PROBLEM $it")
        problemAdapter.submitData(it)
    }
    searchViewModel.areas.onEach {
        println("RESULT AREAS $it")
        areaAdapter.submitData(it)
    }

**Expected behavior 💭**
I expect that my flow are called when a type a query 

**Environment:**
 - OS: Mac M1 
 - Library Version 3.1.4

**Additional context**
Transformer (in Paginator) is never called, it's not just a flow/livedata issue 

[aallam]

Hi @GautierLouis, that's because you are using onEach, which is an intermediate operator, your flow never starts.
From Flow documentation:

Intermediate operators on the flow such as map, filter, take, zip, etc are functions that are applied to the upstream flow or flows and return a downstream flow where further operators can be applied to. Intermediate operations do not execute any code in the flow and are not suspending functions themselves.

What you need is a terminal operator to trigger the flow to start listening for values, such as collect. The simplest way would using LifecycleScope:

lifecycleScope.launch {
    searchViewModel.problems.collect {
        println("RESULT PROBLEM $it")
        problemAdapter.submitData(it)
    }
    searchViewModel.areas.collect {
        println("RESULT AREAS $it")
        areaAdapter.submitData(it)
    }
}

[GautierLouis]

Hi @aallam ,
Thanks. I did, I wasn't using flow correctly. But it still not working.
problemPaginator does his transformation but I only got 1 data collected in my flow
areaPaginator isn't called at all
When I enter a query, nothing change (no transformation)

[aallam]

Hi @GautierLouis, indeed paging3 and multisearch doesn't seem to work as expected, we have added this issue to our backlog.
I would suggest either using two HitsSearchers or don't use pagination like in this example, or this one for compose.

[GautierLouis]

No worries, I've managed to do it with a basic subscriptions + flow, and I don't have any skills on compose yet.
Let me know when it will be fixed. thanks for your time :)