I have database query that returns the list of indexes of objects for a certain day, i.e.:
getIndexesOfDay(day: Day): Flow<List<String>>
Now, I need to listen for details for each index, for instance:
getDetailsByIndex(index: String): Flow<Details>
So the question is: how can I accomplish this using Flows?
Two important constraints:
Details object should also update the flow.What I have already tried:
getIndexesOfDay(todayDay)
.map { indexes ->
indexes?.map {
mIndex->
getDetailsByIndex(mIndex)
}
}
But it returns a Flow<List<Flow<Details>>> instead of the desired Flow<List<Details>>
Appreciate any help!
I haven't tested this, but I believe it should be possible using flatMapLatest() and combine():
getIndexesOfDay(todayDay)
.flatMapLatest { indexes ->
combine(indexes.map { getDetailsByIndex(it) }) { it.asList() }
}
For each new list of indexes, it invokes getDetailsByIndex() multiple times to acquire a list of flows and then combines these flows into a single flow of details lists.
The drawback is that whenever indexes change, it throws away all Flow<Details> objects, even if an index existed in both old and new list of indexes. It would be probably better to create some kind of a cache of detail flows per each index.