Hi, I'm trying to update my state with reducer. The only way I was able to achieve that was by using...

# compose

[than_]

Hi, I'm trying to update my state with reducer. The only way I was able to achieve that was by using ViewModel and collectAsState but by doing that I lost the ability to change state in the interactive mode in android studio. Is there something I'm missing?

[Zach Klippenstein (he/him) [MOD]]

Not quite sure what you’re seeing - when running your compose preview in interactive mode, updates to your view model State are not triggering recomposition?

[than_]

Yes, that's the case. Should have been clearer, sorry.

[Zach Klippenstein (he/him) [MOD]]

I’m very much just guessing here, but since the interactive preview isn’t running a real environment, it might be doing something weird with the view model provider - maybe the fake provider isn’t memoizing correctly or something?

[than_]

Yeah seems like it. I've tried to make it work without ViewModel using something like this

[than_]

Untitled

[than_]

that does not update the state at all 😕

[Zach Klippenstein (he/him) [MOD]]

are you `remember`ing that?

[than_]

sure, call site looks like this:

val (stt, dispatch) = remember { reducerStateOf(1, ::reducer) }

[Zach Klippenstein (he/him) [MOD]]

Wouldn’t you want to return a State<STATE> in that pair? Right now you’re just returning the initial state value as the raw value, which means it has no way to be updated after being memoized by remember

[Zach Klippenstein (he/him) [MOD]]

so e.g.

fun <ACTION, STATE> reducerStateOf(initialValue: STATE, reducer: Reducer<ACTION, STATE>): Pair<State<STATE>, Dispatch<ACTION>> {
    val state = mutableStateOf(initialValue)

    val dispatch: Dispatch<ACTION> = {action: ACTION ->
        val newState = reducer(action, state.value)
        state.value = newState
    }

    return state to dispatch
}

[Zach Klippenstein (he/him) [MOD]]

i’m guessing that’s why you’re not seeing changes

[than_]

Yep that was it 🙂 thank you very much