Hi all! I’m trying to use `NativeCoroutinesState` in <KMP-NativeCoroutines> library. But even when I...

# multiplatform

[ken_kentan]

Hi all!
I’m trying to use NativeCoroutinesState in KMP-NativeCoroutines library.
But even when I update a StateFlow, it won’t trigger re rendering in SwiftUI side…
Does anyone can help about it?

[ken_kentan]

Swift code:

struct ContentView: View {
	let greet = Greeting().greet()

	@StateViewModel var viewModel = HomeViewModel()

	var body: some View {
        VStack {
            Text(viewModel.uiState.text)
            Button(
                action: {
                    print(viewModel.uiState)
                    viewModel.onClick()
                    print(viewModel.uiState)
                }
            ) {
                Text("Button")
            }
        }
	}
}

Log:

HomeUiState(text=5)
onClick: current HomeUiState(text=5)

[ken_kentan]

Text(viewModel.uiState.text) should show 5, but still keep showing initial state (0)

[Rick Clephas]

Hi! Could you share a code snippet of the ViewModel?

[Rick Clephas]

In order for state changes to propagate to SwiftUI you'll need to use KMM-ViewModel functions in your VM.
The NativeCoroutinesState annotation alone just exposes the StateFlow as a property.

[ken_kentan]

Hi! Here is the ViewModel code:

class HomeViewModel: KMMViewModel() {

    @NativeCoroutinesState
    val uiState = MutableStateFlow(HomeUiState())

    init {
        viewModelScope.coroutineScope.launch {
            while (true) {
                delay(1000)
                uiState.update {
                    it.copy(count = it.count + 1)
                }
            }
        }
    }

    fun onClick(): HomeUiState {
        println("onClick: current ${uiState.value}")
        uiState.update {
            it.copy(count = 0)
        }

        return uiState.value
    }
}

[Rick Clephas]

Thanks the following should work:

val uiState = MutableStateFlow(viewModelScope, HomeUiState())

Providing the viewModelScope to the StateFlow will make sure that any changes are propagated to SwiftUI.

[Rick Clephas]

Note: you’ll need to add the following import for that:

import com.rickclephas.kmm.viewmodel.MutableStateFlow

[ken_kentan]

Ah! So I need to use KMM’s MutableStateFlow.
Thank you! It working well now!
I would be very appreciate if you can update the README to note about it!

[Rick Clephas]

It’s already on my todo list to improve the documentation around those functions 😇