I have a `List` of `Flow`s which I combine into a ...

# coroutines

[Mark]

I have a List of `Flow`s which I combine into a single Flow using combine(Iterable) . Now I want to add another Flow to the List . How to handle this? Keep a reference to the combine Job and cancel/recreate accordingly? Combine the existing combine Flow with the new Flow list item? Or perhaps represent the list as a Flow and use runningFold and flatMapLatest? Something else?

[Odife K]

At what point do you want to add another flow? After the combine? Is it not possible to add it upstream with the original list?

[Mark]

I have a MutableList of items where each item is represented by a Flow. So I combine these `Flow`s into one Flow . The items are being appended to as the user scrolls down and so at this point I need to recreate the combined flow. I’m just wondering the best way to do this.

[Odife K]

Then I suppose a single flow runningFold would be most suited for this situation. Or any other operator that can give you the latest item plus previous combination.

[Mark]

I ended up replacing the MutableList with a MutableStateFlow starting with an empty list, and using update whenever I wanted to add a new item. Then I use flatMapLatest and combine to get the flow I need. Note: it’s important to not use combine when the list is empty. Something like this:

val itemsStateFlow = MutableStateFlow(emptyList<Item>())

fun addItem(item: Item) {
    itemsStateFlow.update { it + item }
}

val resultsFlow: StateFlow<Foo> = itemsStateFlow.flatMapLatest { items ->
    if (items.isEmpty()) {
        flowOf(Foo(emptyList()))
    } else {
        combine(items.map(Item::flow)) {
            Foo(it)
        }
    }
}.stateIn(coroutineScope, SharingStarted.Eagerly, Foo(emptyList())