RxReduceReducers.swift

func userReducer (state: AppState?, action: Action) -> AppState {

    var currentState = state ?? AppState(userState: UserState.empty, 
                                         contactsState: ContactsState.empty)

    // according to the action we create a new state
    switch action {
    case let action as LoadUserAction:
        currentState.userState = UserState.loaded(User(firstname: action.firstname, 
                                                       lastname: action.lastname))
        return currentState
    default:
        return currentState
    }
}

func contactsReducer (state: AppState?, action: Action) -> AppState {

    var currentState = state ?? AppState(userState: UserState.empty,
                                         contactsState: ContactsState.empty)

    // according to the action we create a new state
    switch action {
    case let action as LoadContactsAction:
        currentState.contactsState = ContactsState.loaded(action.contacts)
        return currentState
    default:
        return currentState
    }
}