How to create a ReplaySubject with RxCpp?

Question

In my c++ project, I need to create Subjects having an initial value, that may be updated. On each subscription/update, subscribers may trigger then data processing... In a previous Angular (RxJS) project, this kind of behavior was handled with ReplaySubject(1).

I'm not able to reproduce this using c++ rxcpp lib.

I've looked up for documentation, snippets, tutorials, but without success.

Expected pseudocode (typescript):

private dataSub: ReplaySubject<Data> = new ReplaySubject<Data>(1);

private init = false;

// public Observable, immediatly share last published value
get currentData$(): Observable<Data> {

    if (!this.init) {
      return this.initData().pipe(switchMap(
        () => this.dataSub.asObservable()
      ));
    }
    return this.dataSub.asObservable();
  }

Answer 1

I think you are looking for rxcpp::subjects::replay. Please try this:

    auto coordination = rxcpp::observe_on_new_thread();
    rxcpp::subjects::replay<int, decltype(coordination)> test(1, coordination);

    // to emit data
    test.get_observer().on_next(1);
    test.get_observer().on_next(2);
    test.get_observer().on_next(3);

    // to subscribe
    test.get_observable().subscribe([](auto && v)
        printf("%d\n", v); // this will print '3'
    });