I have a `MutableStateFlow lt Map lt gt gt ` what s the most kotlinlang #coroutines

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Title

w

William Reed

07/09/2021, 12:30 PM

I have a

MutableStateFlow<Map<..., ...>>

what’s the most idiomatic way to mutate the map and update the

StateFlow

? seems like I need to make a copy of the current value and then update it? something like this seems verbose and awkward

stateFlow.value = stateFlow.value.toMutableMap().apply { … modify …}

i could do this

inline fun <K, V> MutableStateFlow<MutableMap<K, V>>.mutate(mutation: (MutableMap<K, V>) -> Unit) {
    val newValue = value.toMutableMap()
    mutation(newValue)
    value = newValue
}

and usage would just be

stateFlow.mutate {
  ... modify ...
}

m

melatonina

07/09/2021, 1:29 PM

It's the same problem as replacing any observable collection with

StateFlow

, for example when using a

RecyclerView

on Android. Inexplicably, I never saw this addressed anywhere. I'm not an expert, though.

n

Nick Allen

07/12/2021, 5:35 AM

I suggest

MutableStateFlow<Map<K, V>>

. You can update it with just

stateFlow.value += item

or something similar. If you need more complicated mutations, then i think you are stuck with more complicated code.

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