Throttle only if specific condition met

问题

I have an observable that I am subscribing on. This obsevable will be returning an object that has a property called ActivationType that can be set multiple times.

What I am trying to achieve is log a message whenever ActivationType is set to "Type1". However, if ActivationType is set to "Type2", log the message only once and wait for 30 seconds before logging again if ActivationType is "Type2".

So if I have:

myObservable
    .Where(o => o.ActivationType == "Type1" || o.ActivationType == "Type2")  //listen for types 1 and 2
    .Throttle() // ??? somehow only throttle if we are currently looking at Type2
    .Subscribe(Log); //log some stuff

I believe Throttle() is what I am looking for but am not sure how to trigger it conditionally.

Any suggestions?

回答1:

Ah, a perfect case for the near-impossible-to-understand Window operator!

EDIT: I post this link like a dozen times a month, I swear - best read-thru I've seen of the Window, Join, Buffer, GroupJoin, etc. operators:

Lee Campbell: Rx Part 9–Join, Window, Buffer and Group Join

var source = new Subject<Thing>();

var feed = source.Publish().RefCount();
var ofType1 = feed.Where(t => t.ActivationType == "Type1");
var ofType2 = feed
    // only window the type2s
    .Where(t => t.ActivationType == "Type2")
    // our "end window selector" will be a tick 30s off from start
    .Window(() => Observable.Timer(TimeSpan.FromSeconds(30)))
    // we want the first one in each window...
    .Select(lst => lst.Take(1))
    // moosh them all back together
    .Merge();

    // We want all "type 1s" and the buffered outputs of "type 2s"
    var query = ofType1.Merge(ofType2);

    // Let's set up a fake stream of data
    var running = true;
    var feeder = Task.Factory.StartNew(
       () => { 
         // until we say stop...
         while(running) 
         { 
             // pump new Things into the stream every 500ms
             source.OnNext(new Thing()); 
             Thread.Sleep(500); 
         }
    });

    using(query.Subscribe(Console.WriteLine))
    {               
        // Block until we hit enter so we can see the live output 
        // from the above subscribe 
        Console.ReadLine();
        // Shutdown our fake feeder
        running = false;
        feeder.Wait();
     }

回答2:

Why not just use two streams?

var baseStream = myObservable.Publish().RefCount(); // evaluate once
var type1 = baseStream.Where(o => o.ActivationType == "Type1");
var type2 = baseStream.Where(o => o.ActivationType == "Type2").Throttle(TimeSpan.FromSeconds(30));

type1.Merge(type2).Subscribe(Log);

来源：https://stackoverflow.com/questions/15253675/throttle-only-if-specific-condition-met

标签

system.reactive

throttling