With Rx, how do I ignore all-except-the-latest value when my Subscribe method is running

Question

Using Reactive Extensions, I want to ignore messages coming from my event stream that occur while my Subscribe method is running. I.e. it sometimes takes me lon

Answer 1

Here is an attempt using "just" Rx. The timer and the subscriber are kept independent by observing on the threadpool and I've used a subject to provide feedback on completing the task.

I don't think this is a simple solution, but I hope it might give you ideas for improvement.

messages.
    Buffer(() => feedback).
    Select(l => l.LastOrDefault()).
    ObserveOn(Scheduler.ThreadPool).
    Subscribe(n =>
    {
        Thread.Sleep(TimeSpan.FromMilliseconds(250));
        Console.WriteLine(n);
        feedback.OnNext(Unit.Default);
    });

feedback.OnNext(Unit.Default);

There is one slight problem -- the buffer is first closed when it's empty so it generates the default value. You could probably solve it by doing the feedback after the first message.

---

Here it is as an extension function:

public static IDisposable SubscribeWithoutOverlap(this IObservable source, Action action)
{
    var feedback = new Subject();

    var sub = source.
        Buffer(() => feedback).
        ObserveOn(Scheduler.ThreadPool).
        Subscribe(l =>
        {
            action(l.LastOrDefault());
            feedback.OnNext(Unit.Default);
        });

    feedback.OnNext(Unit.Default);

    return sub;
}

And usage:

    messages.SubscribeWithoutOverlap(n =>
    {
        Thread.Sleep(1000);
        Console.WriteLine(n);
    });