Comment by DevMan on "I am Ben Lesh. Ask me anything."

I have an RxJs question that might be good for helping others (and myself) understand RxJS Observables and timing.

Lets say I have a service that looks like so: getData(something){ // ...code return IntervalObservable.create(1000) .flatMap(() => { return this.http.get(url).map(res => //do something with res ); }); }

This is getting called in a component like so: this.data$ = this.MyService.getData(this.something)

A) How would I fire this request to get the response back right away (instead of waiting 1 second) and then wait another 5 seconds to resend the request? B) Let say I want to add other observables to this, and have them all call the service and get data back at the same time. How would I do that? I read some place about hot and cold observables and .share(), but I don't know if that is relevant.

My use case is an app that will allow you to add multiple devices to listen to a server and sync data, but they all need to sync at the same time. I am not sure this is even the best way to do it, but it works so far for one item. Thanks for the guidance!

A) You can use timer instead of interval to send a request right away but have the same effect:

timer(0, 1000);

// which is the same, basically, as:

concat(timer(0), interval(1000))

B) You'd use share or shareReplay which makes the observable multicast, thus "sharing" it's values with many subscribers. Since it's something happening on an interval, I'd use shareReplay(1), because that is going to cache the previous value and give it to a new subscriber right away, instead of them having to wait for the next notification.

timer(0, 100).pipe(
  switchMap(() => this.http.get(url)),
  shareReplay(1),
)

The above approach is what you'd what to do.

BTW: I recommend against using IntervalObservable.create, that's more of an implementation thing from the library, instead import { interval } from 'rxjs/observable/interval';. That will give you a static function to use.

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