Ignore events if another event fires with Rx

Question

In short

Looking for a way to achieve

observableOne.SkipIf(observableTwoFiresWithinPeriod)

Explanation

Let's say I am observing people walking through a door (walkins Observable)
and I also have a way to tell if they have a phone (phoneWalkins Observable).
Now I would like to observe the other piece of the pie of people walking through the door without a phone (nonPhoneWalkins Observable)

Given I have walkins and the phoneWalkins subset available to me as streams then nonPhoneWalkins should be walkins except phoneWalkins.

How to implement that with Reactive Extensions?
Note that phoneWalkins signals just after walkins if the person is found to carry a phone

You can apply the solution from @LeeCampbell to this problem. Just omit the `Where` clause. — supertopi, Mar 28 '16 at 10:02

score 1 · Answer 1 · answered Mar 28 '16 at 09:35

Here is my simple try:

public class Program
    {
        static void Main()
        {
            // all walkins
            var walkins =
                // all persons through a door each second
                Observable.Interval(TimeSpan.FromSeconds(1), Scheduler.CurrentThread)
                // if has phone (is even) then true, if not false
                .Select(i => (i % 2 == 0));

            var phoneWalkins = // substream of phoneWalkins (if you want it separate)
                walkins
                .Where(i => (i == true))
                .Select(i => i);

            var nonPhoneWalkins = // substream of nonPhoneWalkins (if want it separate)
                walkins
                .Where(i => (i == false))
                .Select(i => i);

            //walkins.Subscribe(Console.WriteLine); // output all
            phoneWalkins.Subscribe(Console.WriteLine); // output phone
            //nonPhoneWalkins.Subscribe(Console.WriteLine); // output nonPhone
        }
    }

Unfortunately that is not the situation I have meaning phoneWalkins and nonPhoneWalkins are not directly derivable from walkins i.e. phoneWalkins is an independent measurement source e.g. Bob is hired to count people walking in with phones but a CCTV camera counts walk-ins indiscriminately — Cel, Mar 28 '16 at 09:49

score 1 · Answer 2 · answered Mar 28 '16 at 10:28

Thanks @supertopi for pointing to another relevant question, and the answer of @LeeCampbell there ported to this context should work:

nonPhoneWalkins = 
    walkins.SelectMany
    (walkin => 
        phoneWalkins.Take(1).Select(phoneWalkin => false)
        .Amb(
            Observable.Timer(TimeSpan.FromSeconds(1)).Select(l => true)
            )
    )
    .Where(nonPhoneWalkin => nonPhoneWalkin);

Ignore events if another event fires with Rx

In short

Explanation

2 Answers2