Concat undetermined api call using rxjs

Question

I would like query an Api that returns dada and next item that contains the next url to call.

When next is null it means that all data is sent.

  getData(url?: any) {
    if (!url) {
      url = `https....../geojson/geo/?srid=xxx&code=xx&jsonb_as_text=false&page_size=10`;
    }
    return this.httpClient.get(url, { headers }).pipe(
      flatMap((res: any) => {
        if (res.next) {
          this.getData(res.next);
        }
        return res;
      })
    );
  }

Actually the component only gets the first call but not the second.

How can I chain well api calls and concat the results then?

kvetis · Accepted Answer · 2022-05-18 15:03:07Z

1

You probably want to use expand operator. It is recursive - each response calls the operator callback. You can use toArray to collect all responses as an array. You could use scan or no operator to process immediate results while the others are loading.

getData(url) {
   return this.httpClient.get(url, { headers })
}

getAllData() {
  
    const url = `https....../geojson/geo/?srid=xxx&code=xx&jsonb_as_text=false&page_size=10`;
    
    return this.getData(url).pipe(
      expand((res: any) => {
        if (res.next) {
          return this.getData(res.next);
        }
        return EMPTY;
      }),
      toArray(),
      map(responses => responses.flatMap(response => response.items))
    );
  }

answered May 18, 2022 at 15:03

kvetis

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