Fetching data

MyViewModel.kt

data class MyState(
    /** Use this to render the UI */
    val fetchedGroups: List<Whatever> = emptyList()
    /** Use this to show loading state/errors */
    val groupsRequest: Async<Unit> = Uninitialized
) : MvRxState

class MyViewModel(initialState: MyState) : MvRxViewModel<MyState>(initialState) {

    init {
        fetchGroups()
    }
    
    fun fetchGroups() {
       someObservable.execute { copy(groups = it.map { Unit }, fetchedGroups = it() ?: fetchedGroups) }
    }

  private fun <T, V> Async<T>.map(mapper: (T) -> V) = when (this) {
      Uninitialized -> Uninitialized
      is Loading -> Loading()
      is Success -> Success(mapper(this()))
      is Fail -> Fail(error)
  }
}