什么是 forkJoin 替代方案，它允许并行请求在其中一个失败时完成

Question

I want to run some requests in parallel using forkJoin and combine their results as shown below. However, when one of the requests fails, the rest of the subscriptions are automatically cancelled by the browser. What is a simple alternative to forkJoin that lets me run requests in parallel and if one subscription fails, the rest are allowed to complete?

const posts = this.http.get("https://myApi.com/posts?userId=1");
const albums = this.http.get("https://myApi.com/albums?userId=1");

forkJoin([posts, albums]).subscribe((result) => {
  this.print(result[0], result[1]);
});

print(res1, res2) {
  const message = res1.text + res2.text;
  console.log(message);
}

Answer 1

You can achieve that using forkJoin , however, you have to handle the errors for each sub Observable separately using catchError to prevent canceling the stream if any error occurred.

You can try something like the following:

// import { catchError } from 'rxjs/operators';
// import { forkJoin, of } from 'rxjs';

const posts = this.http
  .get('https://myApi.com/posts?userId=1')
  .pipe(catchError((err) => of(err)));
const albums = this.http
  .get('https://myApi.com/albums?userId=1')
  .pipe(catchError((err) => of(err)));

forkJoin([posts, albums]).subscribe((result) => {
  this.print(result[0], result[1]);
});

Answer 2

I would make a function like

forkJoinReplaceErrors<T,R>(
  observables: Observable<T>[],
  ifError: ObservableInput<R>
) {
  return forkJoin(
    observables.pipe(
      catchError(() => ifError)
    )
  );
}

and then use that instead of forkJoin . Then it's more reusable and can be unit tested.