RXJS/Angular Replace Observable

Question

In an angular interceptor, I want to check wether an auth-token exists. If not, it should be refreshed and the request should be resent.

return next.handle(authReq).pipe(map((result: any) => {
  if (result.body && result.body.error) {
    if (result.body.error === 'ERR_TOKEN_EXPIRED' || result.body.error === 'ERR_TOKENS_DO_NOT_MATCH') {
      console.log('Token is expired or invalid, refreshing.', result.body.error);

      return this.userService.refreshLoginToken().subscribe(success => {
        if (success) {
          return this.intercept(req, next);
        }
      });
    }
  }
  return result;
}));

The Problem is that I don't know how to replace the original Observable returned by next.handle() with a new one. The return statement before this.userService.refreshLoginToken().subscribe() returns a Subscription object. If I just pipe the result of refreshLoginToken() it wont work because refreshLoginToken sends an httprequest which is only executed when there is a subscription.

To reduce the question to a single line: How can I replace the Observable returned in line 1 by next.handle() with the one returned by this.intercept(req, next)?

Thank you!

Does this answer your question? [Angular HTTP interceptor - Cannot return from inner subscription](https://stackoverflow.com/questions/61016241/angular-http-interceptor-cannot-return-from-inner-subscription) — Kurt Hamilton, Apr 04 '20 at 07:46

score 1 · Accepted Answer · answered Apr 04 '20 at 08:07

I think you should do that a bit different way.

please check the example below and the latest switchMap:

import {HttpEvent, HttpHandler, HttpInterceptor, HttpRequest} from '@angular/common/http';
import {Injectable} from '@angular/core';
import {StoreState} from '@core/store';
import {select, Store} from '@ngrx/store';
import {getAuthToken} from '@v2/core/store/auth/auth.reducer';
import {iif, Observable, of} from 'rxjs';
import {switchMap, take} from 'rxjs/operators';

@Injectable()
export class AuthInterceptor implements HttpInterceptor {
    constructor(protected readonly store: Store<StoreState>) {}

    public intercept(request: HttpRequest<void>, next: HttpHandler): Observable<HttpEvent<void>> {
        return this.store.pipe(
            select(getAuthToken),
            take(1),
            switchMap(token =>
                iif(
                    () => !token,
                    of(request),
                    of(
                        request.clone({
                            setHeaders: {
                                Authorization: `Bearer ${token?.accessToken}`,
                            },
                        }),
                    ),
                ),
            ),
            switchMap(clonedRequest => next.handle(clonedRequest)),
        );
    }
}

Thank you! Are the observables created by of() automatically completed when the original http observable completes? — L. Männer, Apr 04 '20 at 08:39
they are completed right after they have emitted all values. but switchMap keeps listening on the main data stream until it has been completed to close the whole sequence. — satanTime, Apr 04 '20 at 08:51

RXJS/Angular Replace Observable

1 Answers1