SavedStateHandleで値の保存と復元が可能な MutableStateFlow

SavableMutableSaveStateFlow.kt

// from https://medium.com/mobile-app-development-publication/saving-stateflow-state-in-viewmodel-2ee9ed9b1a83

class SavableMutableSaveStateFlow<T>(
    private val savedStateHandle: SavedStateHandle,
    private val key: String,
    defaultValue: T
) {
    private val _state: MutableStateFlow<T> =
        MutableStateFlow(
            savedStateHandle.get<T>(key) ?: defaultValue)

    var value: T
        get() = _state.value
        set(value) {
            _state.value = value
            savedStateHandle.set(key, value)
        }

    fun asStateFlow(): StateFlow<T> = _state
}