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How can I map the values of one flow with another that can (or not) be started later? I have flow `A` that will always be there and the flow `B` needs to be started with a id param to observe the database for the specific id, but there may be cases where it will never be init. How can I do this?

My solution was to create a flow `C` that start with an empty value and combines with `A` , then if I ever subscribe to `B` I collect and emit the values to `C`

Could you not also not use a third flow but initialize your flow as you did and also add `.onStart { emit(...) }`? So you first emit something of your liking, and then it will continue emitting more once combine gets new values. Could that work?

I'm not sure I understand you well. The `onStart` would be just to emit a init value? If that's the case I'm just setting it when I start the flow at the moment

Yeah I thought your problem was that your other flow may never start (as you say “or not”) so you never even get an initial emit so it’s stuck waiting forever.

Maybe I just wasn't clear then :sweat_smile: I just mean that in some occasions I need to observe the flow `B` and some other occasions I do not need. So I implemented something similar to what you said, I've a third flow (`C`) and depending on the case I emit to it, otherwise it's just blank and it works fine :slightly_smiling_face:

Perhaps `flatMapLatest` is what you need here? Sorry, your description is not totally clear; perhaps some code could help.