CODEWITHSUNDEEP
c#system.reactive
Jeremy Durnell
Jeremy Durnell

Reputation: 109

Creating an observable that properly dispatches errors?

I'm learning Rx and am working through some of the semantics. As an experiment, I'm building an observable timer that calls OnError on the tenth tick. So far, I have 2 methods that I believe exhibit identical behavior:

var timer = Observable.Interval(TimeSpan.FromMilliseconds(200));

// method 1
Observable.Create<long>(
    x => timer.Subscribe(tick => {
        if (tick == 10)
        {
            x.OnError(new Exception());
        }

        x.OnNext(tick);
    }));

// method 2
timer.Select(x => {
        if (x == 10)
        {
            throw new Exception();
        }

        return x;
    });

Am I correct in assuming that both of these methods will behave exactly the same? If not, what are the differences?

Upvotes: 0

Views: 186

Answers (1)

Ana Betts
Ana Betts

Reputation: 74654

The 2nd way is not equivalent, throwing in a selector results in Undefined Behavior That Might Happen To Look The Same™. Here's a few more ways:

Observable.Interval(TimeSpan.FromMilliseconds(200))
    .Take(9)
    .Concat(Observable.Throw<long>(new Exception("Die!")));

Observable.Interval(TimeSpan.FromMilliseconds(200))
    .SelectMany(x => {
        if (x < 10) return Observable.Return(x);
        return Observable.Throw<long>(new Exception("Die!"));
    });

Upvotes: 1

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