RXJS: request after response

Question

i want to create an observable which handle these:

observable
- http request
- Response
- wait 5 sec and do the request again.

My current function:

  getData (): Observable<CurrentData> {
    return interval(5000)
      .pipe(
        flatMap(() => "HTTP REQUEST",
        ),
        map(this.extractData, this))
  }

but my function are not waiting for the successfull response, my function tries the request every 5 sec.

https://stackoverflow.com/a/42415153/2257128 – rafi muhammad Sep 26 '19 at 11:24 — rafi muhammad, Sep 26 '19 at 11:24

score 2 · Answer 1 · answered Sep 26 '19 at 11:30

user repeat and timer operator, or repeatWhen

  getData (): Observable<CurrentData> {
   return httpRequest().pipe(map(.....),timer(5000),repeat())
  }



  getData (): Observable<CurrentData> {
   return httpRequest().pipe(map(.....),repeatWhen(()=>timer(5000)))
  }

score 0 · Answer 2 · answered Sep 26 '19 at 11:27

You can try the following. First create a BehaviorSubject and an Observable in your Service

private mySubject: BehaviorSubject<any> = new BehaviorSubject<>(null);
myObservable$: Observable<any> = this.mySubject.asObservable();

Then create the the function which will be triggerd once an then goes in an infinite loop.

loop() {
  var that = this;
  this.http.get(myUrl, { headers }).subscribe(
    (data: any) => { 
       this.mySubject.next(data);
       setTimeout(function () {
          that.timeout();
      }, 5000);
  }

Why `setTimeout`? What about a pure `rxjs` way to do this so the code does not have to rely on `window.setTimeout`? — Igor, Sep 26 '19 at 12:33

score 0 · Accepted Answer · answered Sep 26 '19 at 13:34

0

you can use exhaustMap operator , it will ignore until the last one complete

getData (): Observable<CurrentData> {
return interval(5000)
  .pipe(
    exhaustMap(() => "HTTP REQUEST",
    ),
    map(this.extractData, this))
}

answered Sep 26 '19 at 13:34

Fateh Mohamed

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Returns an Observable that emits items based on applying a function that you supply to each item emitted by the source Observable, where that function returns an (so-called "inner") Observable. When it projects a source value to an Observable, the output Observable begins emitting the items emitted by that projected Observable. However, exhaustMap ignores every new projected Observable if the previous projected Observable has not yet completed. Once that one completes, it will accept and flatten the next projected Observable and repeat this process. – KaOBWS Sep 26 '19 at 14:19

RXJS: request after response

3 Answers3