comment_submission_rx_partial.kt

class CommentFormModel(val commentService: CommentService) {
  
  fun formState(
    textChangedEvents: Observable<TextChangedEvent>,
    submitEvents: Observable<SubmitCommentEvent>
  ) : Observable<CommentFormData> {

    // Explicitly declaring the type, for clarity sake
    val requestStateEvents: Observable<Lce<Comment>> = submitEvents
      .switchMap { event -> commentService.submit(event.comment) }
    
    // To use RxJava scan operator, we need to 
    // merge requestStateEvents and textChangedEvents
    val events: Observable<Any> = Observable.merge(textChangedEvents, requestStateEvents)
    // As you can see, we have a problem. The stream data type becomes Any 
   
    return ... 
  }
}