given the following code:

service:

getList(){
    return return this.http.request("put", url_, options_)
}  

component:

submitRequest(reset?){
    this.httpService.getList().subscribe((response) => {
        //if reset return an empty array
        //server cannot return an empty array
    })
}

and I want to do something like:

component:

submitRequest(reset?){
    this.httpService.getList().pipe(someOperator(() => {
        // if reset DO NOT MAKE HTTP CALL BUT INSTEAD RETURN []
    })).subscribe((response) => {
        //IF reset NO SERVER CALL WAS MADE BUT GOT [] FROM someOperator
        //SERVER RESPONSE ONLY IF NO reset
    })
}

how do i achieve this using RXJS ?

CodePudding user response：

something like: if (reset) return of([])?

submitRequest(reset?){
    if (reset) return of([])

    this.httpService.getList().pipe(someOperator(() => {
        // if reset DO NOT MAKE HTTP CALL BUT INSTEAD RETURN []
    })).subscribe((response) => {
        //IF reset NO SERVER CALL WAS MADE BUT GOT [] FROM someOperator
        //SERVER RESPONSE ONLY IF NO reset
    })
}

CodePudding user response：

I would change the reset operator to an Observable<any> that does not emit anything immediately upon subscribing (e.g. not a BehaviorSubject), and then the code can change to:

private destroy$: Subject<void> = new Subject();

ngOnDestroy(): void {
  this.destroy$?.next();
  this.destroy$?.complete();
}

submitRequest(reset?: Observable<any>){
  let o$ = this.httpService.getList();
  if (reset) {
    o$ = merge(o$, reset.pipe(mapTo([])));
  }
  o$.pipe(
    first(),
    takeUntil(destroy$)
  ).subscribe(response => whatever);
}

The subscriber function will

• not be called if your this gets destroyed. Otherwise,
• received an empty array if reset emits anything before the server response is received. Otherwise
• receive the server response.

In any of these cases the subscription will be cancelled so it will clean itself up.