Is there a way to map a

StateFlow<T>

to a

StateFlow<R>

? I have a

MutableStateFlow<MyEnum>

in a view model, but I want it private to expose publicly a

StateFlow<String>

.map

?

It returns a

Flow

, not a

StateFlow

maybe map + stateIn

Not bad. The only problem I have with this is that

stateIn

is a `suspend fun`… So I can’t assign my variable directly like a simple map would allow

How would that work? If it would return a

StateFlow<R>

, how would the

map

function reverse map the latest value from a

T

to an

R

, when assigning a new value to that

StateFlow<R>

if it were implemented by a MutableStateFlow? And this is just for

map

. How would this work for

filter

? Etc.. Using stateIn helps by layering another statefull flow on top of the returned Flow

MutableStateFlow

would need to go backwards, but I don't see a reason why you couldn't map a

StateFlow

backed by a

MutableStateFlow

into something like a

ReadOnlyStateFlow

.

"ReadOnlyStateFlow" is StateFlow, isn't?

I think the only actual implementation of

StateFlow

is

MutableStateFlow

(or rather

StateFlowImpl

, which stores a value). For map support, you would need a new implementation that doesn't store it's own state or support updates. But I think it would be exposed as just

StateFlow

, yeah.

StateFlow is Read only, same as List or Map are read only, not immutable

I thought it was too, but there's actually two classes that implement StateFlow: StateFlowImpl which also implements MutableStateFlow, and ReadonlyStateFlow that doesn't. Of course, ReadonlyStateFlow is just a wrapper around a StateFlow, so it has to be backed by a MutableStateFlow eventually, but I could see map being implemented using it. Any StateFlow implementation that supports map would need a different implementation that updates when it's source does, and wouldn't support writes.

mmap being implemented using it?