how do I map from a ` Mutable StateFlow lt T gt ` to another ` Mutable StateFlow lt T gt ` when I call the `map` method I map the `StateFlow lt T gt ` to a `Flow lt T gt `

how do I map from a ` Mutable StateFlow lt T gt ` to another kotlinlang #coroutines

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Title

andylamax

07/08/2020, 4:16 AM

how do I map from a

(Mutable)StateFlow<T>

to another

(Mutable)StateFlow<T>

? when I call the

map

method I map the

StateFlow<T>

to a

Flow<T>

Tim Malseed

07/08/2020, 4:19 AM

It’s still a

MutableStateFlow

, you’ve just lost the type inference. You could cast your resulting

Flow<T>

as a

MutableStateFlow<>

Zach Klippenstein (he/him) [MOD]

07/08/2020, 4:25 AM

No,

map

does not return a

StateFlow

, it returns a regular

Flow

. You'd need to use something like

stateIn

to convert it back.

☝️ 1

Tim Malseed

07/08/2020, 4:27 AM

Oh, my mistake. I’ll refrain from answering coroutine questions for a few more weeks haha

I assumed that map just operates on the values after they’re emitting, so the underlying flow could still be a

MutableStateFlow

. But I guess that doesn’t make sense, since the Flow’s value type has changed (it emits a different type to the one it receives)

andylamax

07/08/2020, 5:00 AM

Thank you all for your responses

very helpful

Zach Klippenstein (he/him) [MOD]

07/08/2020, 1:48 PM

The reason map can't maintain the

StateFlow

type on its own is explained by Roman in the comments here: https://github.com/Kotlin/kotlinx.coroutines/issues/2081

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