ViewModelStateFlow

BaseViewModel.kt

import androidx.lifecycle.ViewModel
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.StateFlow

sealed class ViewModelStateFlow<T>(stateFlow: StateFlow<T>) : StateFlow<T> by stateFlow

private class ViewModelStateFlowImpl<T>(
        initial: T,
        val wrapped: MutableStateFlow<T> = MutableStateFlow(initial)
) : ViewModelStateFlow<T>(wrapped)

abstract class BaseViewModel : ViewModel() {

    protected fun <T> createViewModelStateFlow(initial: T): ViewModelStateFlow<T> =
            ViewModelStateFlowImpl(initial)

    protected fun <T> ViewModelStateFlow<T>.setValue(value: T): Unit = when (this) {
        is ViewModelStateFlowImpl -> wrapped.value = value
    }
}

SomeFragment.kt

class SomeFragment {
    private val vm = SomeViewModel()

    fun onCreate() {
        val currentValue: Int = vm.flow.value
//        vm.flow.setValue(4)  // compilation error
    }
}

SomeViewModel.kt

import kotlinx.coroutines.delay

class SomeViewModel : BaseViewModel() {
    val flow = createViewModelStateFlow(0)

    suspend fun load() {
        flow.setValue(1)
        delay(1000)
        flow.setValue(flow.value + 1)
    }
}