I have a method that reads an int from datastore (...

# android

[Pablo]

I have a method that reads an int from datastore (which returns FlowInt):

fun readInt(key: String): Flow<Int> {
    return context.dataStore.data.map { preferences -> preferences[intPreferencesKey(key)] ?: 0}
}

And Having this UiState and this ViewModel:

data class UiState(val value: Int = 0)
class ScreenViewModel(): ViewModel() {
    private val _uiState = MutableStateFlow<UiState>(UiState())
    val uiState: StateFlow<nUiState> = _uiState

    init {
        viewModelScope.launch(Dispatchers.IO) {
            val value = CustomDataStoreUtil.readInt("KEY")
            _uiState.value = _uiState.value.copy(value = value)
        }
    }

How can I solve this situation? the datastore readInt returns a Flow<Int> but I need to save just the Int inside my UiState as you can see in my viewmodel

[Seri]

Do you want to read the value from readInt() once and use it for your viewmodel's initial state, or do you want the viewmodel's state to react to new values from your preference store?

[Pablo]

I want to react to new values,

Is it the best option to do this?

CustomDataStoreUtil.readInt("KEY").collect { value -> // Once the value is emitted from the flow, update the UiState _uiState.value = UiState(value = value) }

or to do this?

CustomDataStoreUtil.readInt("KEY").first()

[Pablo]

or another option?

[Seri]

Your first approach should work well! As well, consider using MutableStateFlow.update(...) for better atomic/threadsafe behavior.

https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.flow/-mutable-state-flow/#1996476265%2FFu[…]ns%2F1975948010

[Pablo]

you mean doing this?

init {
    viewModelScope.launch(<http://Dispatchers.IO|Dispatchers.IO>) {
        CustomDataStoreUtil.readInt("KEY").collect { value ->
            _uiState.update { currentState ->
                currentState.copy(value = value)
            }
        }
    }
}

[Pablo]

is that the correct way to use update?

[Pablo]

and also, how long will be alive the collect method?

[Seri]

The collect here will inherit the lifetime of your viewModelScope. Since viewModelScope is a lifetime-aware component, it will respect your viewmodel's lifespan

[Pablo]

thank you Seri