Hi, the `combine` operator only emits once every f...

# coroutines

[Christoph Wiesner]

Hi,
the combine operator only emits once every flow has an emission.
in my case i want to combine flows and it might that one flow would not emit at all - in that case i want to have the transformation receive a null value for not yet existing values of those streams.

combineAlways(flow1, flow2) { v1, v2 (null as not yet an emission) ->
...
}

is there a way to achieve that?

[Trym Nilsen]

Can you wrap flow1 and flow2 in each a flow that always emits an initial null value?

[Christoph Wiesner]

true, i could send a “dummy” value for the stream which potentially does not emit actual values.

[Trym Nilsen]

Are the types from flow1 and flow2 the same or is it different types?

[Christoph Wiesner]

different

[efemoney]

flow2.onStart { emit(null) }?

[efemoney]

combine(
  flow1,
  flow2.onStart { emit(null) },
) { o1, o2? ->
  // ... do your thing
}

[Christoph Wiesner]

yep, that’s a workaround. 👍

[efemoney]

Nitpick but its not a “_workaround”_ 😅, its the K coroutine way

[Christoph Wiesner]

ok - i thought there might be a more elegant solution (operator) to that.
bc. with that i need to make one flow nullable and also need to know which flow potentially does not emit values

[Christoph Wiesner]

but thanks for your help! 🙂