Pause and Resume Subscription on cold IObservable

Question

Using Rx, I desire pause and resume functionality in the following code:

How to implement Pause() and Resume() ?

    static IDisposable _subscripti         


        

Answer 1

Here's a reasonably simple Rx way to do what you want. I've created an extension method called Pausable that takes a source observable and a second observable of boolean that pauses or resumes the observable.

public static IObservable Pausable(
    this IObservable source,
    IObservable pauser)
{
    return Observable.Create(o =>
    {
        var paused = new SerialDisposable();
        var subscription = Observable.Publish(source, ps =>
        {
            var values = new ReplaySubject();
            Func> switcher = b =>
            {
                if (b)
                {
                    values.Dispose();
                    values = new ReplaySubject();
                    paused.Disposable = ps.Subscribe(values);
                    return Observable.Empty();
                }
                else
                {
                    return values.Concat(ps);
                }
            };

            return pauser.StartWith(false).DistinctUntilChanged()
                .Select(p => switcher(p))
                .Switch();
        }).Subscribe(o);
        return new CompositeDisposable(subscription, paused);
    });
}

It can be used like this:

var xs = Observable.Generate(
    0,
    x => x < 100,
    x => x + 1,
    x => x,
    x => TimeSpan.FromSeconds(0.1));

var bs = new Subject();

var pxs = xs.Pausable(bs);

pxs.Subscribe(x => { /* Do stuff */ });

Thread.Sleep(500);
bs.OnNext(true);
Thread.Sleep(5000);
bs.OnNext(false);
Thread.Sleep(500);
bs.OnNext(true);
Thread.Sleep(5000);
bs.OnNext(false);

It should be fairly easy for you to put this in your code with the Pause & Resume methods.