Could anyone try to help me understand something w...

# compose-desktop

[Ryan Smith]

Could anyone try to help me understand something with Flow and Compose? One of the predominant lessons I've been learning is "make your composables stateless by hoisting". I'm trying to adhere to this by exposing as much state as makes sense through properties on my view models.

For example, my data layer has an in-memory Repository that exposes a collection of items through a Flow . My view model is meant to collect that flow as state, and expose that state to my Table composable to be displayed on the screen. But since collectAsState is marked as @Composable I can't call it from my view model. As I see it I could either pass the Flow directly through my view model to my Table composable or stick with mutableStateOf and collect the Flow internally to the view model and just expose the MutableState to my Table.

More generally, though, it feels like the two ideas "state through the view model" and "collectAsState is Composable-only" are at odds here, which makes me think there's "the way" to do this sort of thing that I'm not seeing right now.

[Casey Brooks]

Generally-speaking, collectAsState() is done to connect the reactive Flow into the UI/Compose world. ViewModels, by nature, live above the UI, and so should not be using State<T>, but instead still working with Flow.

So what you’d want to do is have your ViewModel process your Repository’s Flow in some manner, and then expose its own Flow (or StateFlow) which contains the data from the Repository and also the other stuff you’re managing in your ViewModel. And then your Compose code calls collectAsState() on your ViewModel’s Flow, and is completely ignorant of the Repository

[Ryan Smith]

It makes sense that the UI should be completely ignorant of the Repository. I was trying to achieve that by having the view model operate on the Flow from my Repository as you suggested, but then ultimately collect it as well and then expose that result to the UI through some State.

I believed collectAsState to be a convenient way to achieve the last part. Instead it sounds calling collect on a Flow from the UI is not only okay it's a good way to bridge the two worlds. Is that right?

[Kirill Grouchnikov]

These general questions are better posted in #compose that has a bit wider audience and a bit more exposure

[Ryan Smith]

That's a fair point, I can x-post there as well. I initially decided not to to avoid the discussion ending up on Android-specific constructs like ViewModel or LiveData as solutions.