I have a Flow<List<Int?>>
and I want to collect this flow but only until I get a null Int. Then the flow should get cancelled. For example,
val flow = flowOf(
listOf(1, 2),
listOf(3, null),
listOf(4)
)
flow.collectUntilNull {
println(it)
}
The output that I want is:
[1, 2]
[3, null]
I know there is a function Flow.takeWhile
but it doesn't emit the value where predicate returns false. In my case I want that one also.
public fun <T> Flow<T>.takeWhile(predicate: suspend (T) -> Boolean): Flow<T> = flow {
return@flow collectWhile { value ->
if (predicate(value)) {
emit(value)
true
} else {
// I want a "emit(value)" here
false
}
}
}
Since collectWhile
is internal I can't use this code. Although I guess I can copy paste that collectWhile
implementation in my code. But is there another way to do this?
transformWhile
is a more flexible/generalized takeWhile
.
flow
.transformWhile {
emit(it)
myCondition(it)
}
.collect {
println(it)
}