I use Compose’s `fun StateFlow<T>.collectAsS...

# compose

[Miguel Vargas]

I use Compose’s fun StateFlow<T>.collectAsState() without initial value so I don’t have to come up with some empty object while the ui waits for the ViewModel to figure out what should be drawn. But when I want to log each emission it breaks because Flow<T>.collectAsState does require an initial.

class ViewModel {
  val myStateFlow = _myStateFLow
      .onEach { logger.i("check $it out!") } 
   // onEach casts it to Flow, not a StateFlow any more :(
}

Any ideas for a workaround?

[Scott Kruse]

Idk I just define an initial default state now

[knthmn]

In you specific use case, you can launch another coroutine to collect the StateFlow and log the value.

[Steffen Funke]

Can stateIn help? This converts a (cold) Flow into a (hot) StateFlow - also requires an initial value, but you can just use the same there as you have used for _myStateFlow.

Disclaimer: I have not tested if t works the same with an already “hot” StateFlow under the hood - but I’d expect that it should:

class ViewModel {
  val myStateFlow = _myStateFLow
      .onEach { logger.i("check $it out!") }
      .stateIn(viewModelScope, SharingStarted.WhileSubscribed(3000), "Initial value") // you get back a StateFlow!
}

[Steffen Funke]

I guess that is the way to go, as answered here re by @elizarov

The design of stateIn operator (…) fully covers the case of missing state flow operator. Any chain of operators on a state flow can be materialized into another StateFlow using stateIn operator,