savedMutableStateFlow

SavedMutableStateFlow.kt

fun <T> ViewModel<*>.savedMutableStateFlow(
  initialValue: T,
  key: String? = null,
): ReadOnlyProperty<ViewModel<*>, MutableStateFlow<T>> {
  var mutableStateFlow: MutableStateFlow<T>? = null

  return ReadOnlyProperty { _, property ->
    if (mutableStateFlow != null) {
      return@ReadOnlyProperty mutableStateFlow!!
    }

    return@ReadOnlyProperty synchronized(this) {
      if (mutableStateFlow != null) {
        return@synchronized mutableStateFlow!!
      }

      val propertyName = key ?: property.name
      val flowInitialValue = state.get<T>(propertyName) ?: initialValue

      MutableStateFlow(flowInitialValue).also { flow ->
        flow
          .onEach { newValue -> state[propertyName] = newValue }
          .launchIn(viewModelScope)

        mutableStateFlow = flow
      }
    }
  }
}