Rx observable which publishes a value if certain timeout expires

Question

I have a method that returns an observable. This observable should (if evetything is working right) publish a value each second. What I would like to do is have it publish

Answer 1

Here is a way. Starts a timer which will yield "bad" when it expires. Each time your statusProvider produces a status, the timer gets reset.

var statusSignal = statusProvider
            .Subscribe(statusKey)  //returns an IObservable
            .Select(st => st.ToUpper())
            .Publish()
            .RefCount();

// An observable that produces "bad" after a delay and then "hangs indefinately" after that
var badTimer = Observable
    .Return("bad")
    .Delay(TimeSpan.FromSeconds(30))
    .Concat(Observable.Never());

// A repeating badTimer that resets the timer whenever a good signal arrives.
// The "indefinite hang" in badTimer prevents this from restarting the timer as soon
// as it produces a "bad".  Which prevents you from getting a string of "bad" messages
// if the statusProvider is silent for many minutes.
var badSignal = badTimer.TakeUntil(statusSignal).Repeat();

// listen to both good and bad signals.
return Observable
    .Merge(statusSignal, badSignal)
    .DistinctUntilChanged()
    .Replay(1)
    .RefCount();