A helper function to let you expose a MutableStateFlow from a SavedStateHandle.

SavedStateHandle+StateFlow.kt

/**
 * Returns a [StateFlow] that access data associated with the given key.
 *
 * @param scope The scope used to synchronize the [StateFlow] and [SavedStateHandle]
 * @param key The identifier for the value
 * @param initialValue If no value exists with the given [key], a new one is created
 *  with the given [initialValue].
 *
 * @see SavedStateHandle.getLiveData
 */
fun <T> SavedStateHandle.getStateFlow(
    scope: CoroutineScope,
    key: String,
    initialValue: T
): MutableStateFlow<T> {
    val liveData = getLiveData(key, initialValue)
    val stateFlow = MutableStateFlow(initialValue)

    // Synchronize the LiveData with the StateFlow
    val observer = Observer<T> { value ->
        if (stateFlow.value != value) {
            stateFlow.value = value
        }
    }
    liveData.observeForever(observer)

    stateFlow.onCompletion {
        // Stop observing the LiveData if the StateFlow completes
        withContext(Dispatchers.Main.immediate) {
            liveData.removeObserver(observer)
        }
    }.onEach { value ->
        // Synchronize the StateFlow with the LiveData
        withContext(Dispatchers.Main.immediate) {
            if (liveData.value != value) {
                liveData.value = value
            }
        }
    }.launchIn(scope)

    return stateFlow
}

As per the documentation inside kotlinx.coroutines.flow.MutableStateFlow.value:
"Setting a value that is [equal][Any.equals] to the previous one does nothing."
Doesn't that mean that this is redundant?

if (stateFlow.value != value) {
    stateFlow.value = value
}

and can be replaced with:

stateFlow.value = value

And with that said, are you aware if any library maintains this function? It's kind of hard to share and have people to use this as a gist.

Hey @StylianosGakis.

Yes, based in the documentation you posted you can remove the if-else.

About a library, I'm not familiar with any but I guess it is simpler to write a custom function in each project for that - I expect Google to add flow support to SavedStateHandle at some point in the future.

Great helper function, thanks!

Would it be an idea to make T : Parcelable?

Hey @PatrickKuijpers, that would work but keep in mind you would block those functions to be used with primitives and other supported types (such as lists), I think. That isn't a problem per see, so go ahead if these are the only types you need in your project.