What's the elegant way to have something like `combine(flow1, flow2, ..., flowN, transform)` that do...

# coroutines

[natario1]

What's the elegant way to have something like combine(flow1, flow2, ..., flowN, transform) that does not wait for all flows to emit the first value? I'd happily receive a smaller array if some flow does not have a value yet.

[elizarov]

You can do onStart { emit(null) } on each on the source flows to have them immediately emit a null. What are you trying to achieve, though?

[natario1]

Yeah I might be doing things the wrong way? I have a List<Flow<T>> where each flow retrieves a single T item. Retrieval is very expensive. Then I want a Flow<List<T>> including all items that satisfy a certain condition, so I'm using combine(*flows) { it.filter(condition) }. Works but, waits for all flows, while I'd like to receive incomplete results as well.

[natario1]

Is onStart { emit(null) } equivalent to flow { emit(null); emitAll(flow) } ?

[elizarov]

It might be easier just to do list.asFlow().flattenMerge(list.size).filter { … }

[natario1]

Thanks. I think that works great if the source flows are guaranteed to emit just once, but what I have is state flows which might emit updated values of T over time