Is there a elegant way to reemit the last value of...

# coroutines

[ursus]

Is there a elegant way to reemit the last value of a flow when same some other signal happens?

currently I have a mutable state flow where I emit a negation (to be unique) so combine reemits

combine(myFlow, reEmitTrigger) { v, _ -> v)

val reEmitTrigger = MutableStateFlow(false)

reEmitTrigger.value = !reEmitTrigger.value

works but .. ugly

[Rob]

Why would you need to re-emit?

[ursus]

In my case I need time as a flow, but obviously I dont want to emit every nanosecond, so I have this workaround to "pull" current time instead, but to "refresh" it I need to reemit the last value, so it then gets mapped with the current time

myFlow
.map { someMapper(it, clock.nowMillis() }

[Rob]

Hmm. Maybe a MutableStateFlow that is updated every tick will work here?

[ursus]

I had that but I'd rather have the time at mapping time, if I pop it into a stateflow, it wont get combined with myFlow in a instant, there is some delay

[Rob]

Would this work for you?

Untitled.kt

[ursus]

not really, what does that solve? it emits current time every 100ms

[Rob]

I thought you wanted "time as flow".

[ursus]

in theory yes, but every 100ms is wasteful

I only "need" it to emit when some condition changes

[Rob]

Would this work for you?

Untitled.kt

[Rob]

Maybe this too. Otherwise I need more context.

Untitled.kt

[Rob]

As far I know there is no RxJava sample operator for kotlin flows.

[Rob]

Flows can emit the same value twice like in this example.

Untitled.cpp

[Stylianos Gakis]

I only “need” it to emit when some condition changes

Then collect that “condition” changes, and at the collection do a System.currentTimeMillis() to see the time which that change happened.

thingFlow.collect { myCondition ->
  val timeOfChange = System.currentTimeMillis()
  // use myCondition and the time of change.
}