Hello, I'm using <@U01EMBJSZHA>'s library for view...

# multiplatform

[AndreiBogdan]

Hello, I'm using @Rick Clephas's library for view models combined with the KMP-NativeCoroutine library so I can use StateFlow on iOS. The problem I'm having is it seems it doesn't want to work with generics.
I have the below (focus on uiState ):

open class BaseViewModel<U, R> internal constructor(
    uiStateDefault: U,
    private val redirectTypeDefault: R
) : KMMViewModel() {

    protected val redirectBehaviorSubject = BehaviorSubject(Redirect(redirectTypeDefault))

    protected val uiStateMutable = MutableStateFlow(viewModelScope, uiStateDefault)

    @NativeCoroutinesState
    val uiState: StateFlow<U> =uiStateMutable.asStateFlow()

    val redirectObservable: ObservableWrapper<Redirect<R>> =
        redirectBehaviorSubject.wrap()
    
    // ....
}

and while on Android it WORKS, on iOS it doesn't. It does see the uiState but it's seen as Any? and iOS needs to cast it to whatever U is in order for it to work.

Is it a limitation of the NativeCoroutine library; am I using it wrong ?!; is it a limitation of KMM itself ?! I would like not to define uiState on each viewModel subclass so iOS can see it properly ... does anyone have an idea how to solve this and keep it generic ? :(

[Rick Clephas]

Yeah that is indeed a limitation. KMP-NativeCoroutines generates extensions functions which don’t support generics.

Since you are using NativeCoroutinesState and just need the actual value you can do the following manually:

@HiddenFromObjC
val uiState: StateFlow<U> =uiStateMutable.asStateFlow()

@ObjCName("uiState")
val uiStateValue: U get() = uiState.value

[Rick Clephas]

This is basically what is normally generated as an extension property, but as a member property which solves the generics limitation

[AndreiBogdan]

hmm, but that will not trigger a recompose when the value changes, will it ?

[AndreiBogdan]

recompose or whatever the swiftUI thing is called 😄 I think it's a view ... anyway ..

[Rick Clephas]

State changes will still be propagated to Swift(UI)

[Rick Clephas]

The magic for that is in MutableStateFlow(viewModelScope, uiStateDefault)

[AndreiBogdan]

ah, ok!

[Rick Clephas]

Once you update the value of that MutableStateFlow the changes are propagated to Swift

[AndreiBogdan]

that's awesome then !!

[AndreiBogdan]

trying it right now ! thank you very much !

[AndreiBogdan]

hmm, so .. i just realized, i don't even need the @NativeCoroutinesState annotation then ...

[Rick Clephas]

Correct. It is just an easy way to create the value property for 99% of the cases.

[AndreiBogdan]

fingers crossed! thank you

[AndreiBogdan]

woot. it worked! the only thing is that it sees it a nullable even though it's always got a default value.
ios dev needs to use uiState?.someField ... Not sure if there's anything I can do about that though 🤔

[Rick Clephas]

Hmm good question, Maybe the following?: BaseViewModel<U: Any, R>

[Michael Krussel]

The interop with Objective-C doesn't handle nullable generics in general, so I've avoided it in all my public generics.

[AndreiBogdan]

@Rick Clephas i forgot to mention, setting U: Any worked perfectly ! Thank you !