Rx CombineLatest with more than two streams

Question

I need to know when the latest value from 4 observable streams match a predicate.

For only two streams, I could use CombineLatest with Where.

How would I achieve this with n>2 streams.

Thanks.

Edit: Answer for what I was trying to achieve

void Main()
{
    var s1 = Observable.Interval(TimeSpan.FromMilliseconds(50));
    var s2 = Observable.Interval(TimeSpan.FromMilliseconds(60));
    var s3 = Observable.Interval(TimeSpan.FromMilliseconds(70));
    var s4 = Observable.Interval(TimeSpan.FromMilliseconds(80));

    Observable.CombineLatest(s1, s2, s3, s4)
        .Where(xs => xs.All(x => x > 10 && x < 20))
        .Subscribe(x =>
        {
            x.Dump();
        });
}

There is an Rxx extension from [this answer](http://stackoverflow.com/a/18834468/337065) that will do what you want. — Matthew Finlay, Dec 09 '15 at 01:39
Thanks for that. I've had a quick flick through the Rxx code. Looks like a library worth knowing. — Damien Sawyer, Dec 09 '15 at 03:47

score 3 · Accepted Answer · answered Dec 09 '15 at 08:48

I think you can still use CombineLatest or perhaps I'm missing your requirements.

[TestMethod]
    public void GreaterThan2StreamsCombineLatest()
    {
        //Arrange
        var s1 = Observable.Return(1).Concat(Observable.Return(10));
        var s2 = Observable.Return(2);
        var s3 = Observable.Return(3);

        var expected = "They're all greater than 1";
        var result = string.Empty;

        //Act
        Observable.CombineLatest(s1, s2, s3)
            .Where(xs => xs.All(x => x > 1))
            .Subscribe(x =>
            {
                x.ToList().ForEach(Console.WriteLine);
                result = "They're all greater than 1";
            });

        //Assert
        Assert.AreEqual(expected, result);
    }

Awesome! I didn't realize there was that overload. Your example is close. I'll post an answer with what I knocked up in Linqpad. Thanks for your time. — Damien Sawyer, Dec 09 '15 at 13:01

Rx CombineLatest with more than two streams

1 Answers1