When working in the ViewModel with Compose, which ...

# compose

[Pablo]

When working in the ViewModel with Compose, which is the difference between working with var myVar by _mutableStateOf_("") and var myVar = _MutableStateFlow_("") and why should I choose one? In theory as I can see both works for observe changes in the state of the application managing those variables in the ViewModel and generate recompositions, but working with by mutableStateOf is way more simple, light and easy than working with MutableStateFlow but everywhere I can see samples with MutableStateFlow and not by mutableStateOf. What I'm losing?

[Alex Vanyo]

https://developer.android.com/topic/architecture/ui-layer/state-production has examples of each and has more info on when you might choose one over the other.

You are absolutely right that both MutableStateFlow and mutableStateOf each provide a observable, mutable container of state.

The main difference is the system in which they operate, which influences how you can interact and combine them - MutableStateFlow operates with the Flow APIs, and mutableStateOf operates in Compose's snapshot state system.

The two systems are distinct, but there are also tools to cross between them - like snapshotFlow (Compose snapshot state -> Flow) and collectAsState / collectAsStateWithLifecycle (Flow -> Compose snapshot state)

[Alex Vanyo]

> but working with by mutableStateOf is way more simple, light and easy than working with MutableStateFlow
If that is what you're finding, then by all means you can prefer to use that. If your ViewModel is only being used to drive Compose UI, there's no technical reason why you have to use just one or the other. I also personally prefer to stay in the Compose state system as much as I can.

[Pablo]

great answer, thank you, maybe can you tell me a simple example of a situation in which MutableStateFlow become necessary over mutableStateOf to reach the functionality?

[Chrimaeon]

As said, it’s not about functionality. By using mutableStateOf you make your view model depend on the compose library. So if you want to have a more independent view model you should rather use the flow.

[Pablo]

I understand, thanks

[Stylianos Gakis]

Funnily enough, if you want to have a more generic ViewModel, compose won't even likely be your issue, since that's perfectly multiplatform, it'd be the ViewModel class itself which isn't yet 😅
I feel like fear for "making it more generic" really isn't a real concern for almost everybody, so feel free to just do it if it works for you.