With Flow what is the "nicest" way to chain two ne...

# flow

[joakim]

With Flow what is the "nicest" way to chain two network requests where the second depend on data from the first?

[wasyl]

a flatMap? Although network requests would usually return just a single value so maybe you can just use suspend fun?

[joakim]

need to mull it over some more. I have a working solution which collects the first flow, requests the second data and then emits a combined result. but it doesn't feel that neat.

[wasyl]

Well, again if it’s just one value then simple

val firstResponse = api.firstRequest()
return api.secondRequest(firstResponse.id)

would work fine. If you need flows for some reason, then I think

api.firstRequest()
  .flatMap { api.secondRequest(it.id) }

is the most idiomatic way

[joakim]

So I have two repositories, each fetching some data.
I have a useCase which integrates with each repository to get this data.

So essentially the usecase is handline two flows and needs to merge that data into one flow in a VM.

If that makes sense?

[joakim]

I currently, in the usecase, just .collect the data from the first api and then collect the data from the second api and then emit a new flow to the viewmodel

[joakim]

suspend fun execute(input) : Flow<Output> {
    return flow {
        repo1.getdata1.collect {
            repo2.getData2.collect {
                emit(CombinedData())
            }
        }
    }
}

[joakim]

pseudocode

[joakim]

which doesn't feel like the most idiomatic way of dealing with it to be honest 😄

[wasyl]

ah, if you can make both requests in parallel then you might want combine(flow1, flow2) { result1, result2 -> }

[treatmaster]

your question is the same with me above. flow B will depend on flow A at some point in future. You could view my issue at here, it solved. https://github.com/Kotlin/kotlinx.coroutines/issues/2548