CODEWITHSUNDEEP
c#timersystem.reactivereactive-programming
Balraj Singh
Balraj Singh

Reputation: 3471

How to impelment dynamic time interval in Reactive Extension

I have a scenario where timer interval changes on every tick event. As shown in below code:

    Timer tmrObj = new Timer();
    tmrObj.Interval = TimeSpan.FromSeconds(11);
    tmrObj.Tick += TimerTickHandler;

   public void TimerTickHandler(EventArg arg)
   {
     tmrObj.pause();

     var response = MakeSomeServiceCall();
     tmr.Interval = response.Interval;

     tmrObj.resume();
   }

If I need to implement Timers in Rx for the same. I can achieve using Timer function. But how can I manipulate Interval on event tick as shown in the above code. The current timer interval implementation is as below:

var serviceCall = Observable.FromAsync<DataResponse>(MakeServiceCall);
var timerCall = Observable.Timer(TimeSpan.FromSeconds(100));

var response = from timer in timerCall
               from reponse in serviceCall.TakeUntil(timerCall)
               .Select(result => result);

Upvotes: 0

Views: 893

Answers (1)

paulpdaniels
paulpdaniels

Reputation: 18663

You can use Generate to handle the data generation if it is a non-async generation. If your method is going to being using async though you can roll your own GenerateAsync method:

public static IObservable<TOut> GenerateAsync<TResult, TOut>(
    Func<Task<TResult>> initialState,
    Func<TResult, bool> condition,
    Func<TResult, Task<TResult>> iterate,
    Func<TResult, TimeSpan> timeSelector,
    Func<TResult, TOut> resultSelector,
    IScheduler scheduler = null) 
{
  var s = scheduler ?? Scheduler.Default;

  return Observable.Create<TOut>(async obs => {

    //You have to do your initial time delay here.
    var init = await initialState();
    return s.Schedule(init, timeSelector(init), async (state, recurse) => 
    {
      //Check if we are done
      if (!condition(state))
      {
        obs.OnCompleted();
        return;
      }

      //Process the result
      obs.OnNext(resultSelector(state));

      //Initiate the next request
      state = await iterate(state);

      //Recursively schedule again
      recurse(state, timeSelector(state));

    });
  });
}

See the original answer

You can use it like so:

var timeStream = ObservableStatic.GenerateAsync(
  () => MakeServiceCall(),
  _ => true,
  _ => MakeServiceCall(),
  result => result.Interval,
  _ => _);

Upvotes: 1

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