RxJS forkJoin handle error on route resolve

Question

I can't seem to figure out a way to catch/handle errors inside forkJoin while trying to do route resolve.

I've created a route resolver for Account page and It should return 2 requests before routing. Now here is the part I cant work out: If user doesn't have a subscription then 404 is returned from server. I would like to handle this and if it happens, user should be routed to a different page, from where he could make subscription.

import { Injectable } from '@angular/core';
import { Resolve, ActivatedRouteSnapshot } from '@angular/router';
import { Observable } from 'rxjs/Rx';
import { AccountService } from './account.service';

@Injectable()
export class AccountResolver implements Resolve<any> {
    constructor(private accountService: AccountService) { }

    resolve(route: ActivatedRouteSnapshot): Observable<any> {
        return Observable.forkJoin([
            this.accountService.getUser(),
            this.accountService.getUserSubscriptions()
        ]);
    };
}

How do I catch and handle error 404 sent by server when getUserSubscriptions() is requested?

Answer 1

This depends where the error happens which is not entire obvious from your example.

If the getUserSubscriptions() call emits an error then you need to catch it before passing this to forkJoin because otherview the forkJoin will reemit the error. Also note that forkJoin requires each source Observable to emit at least one value. This is why I can't use Observable.empty() and I need to use for example Observable.of(null).

return Observable.forkJoin([
    this.accountService.getUser(),
    this.accountService.getUserSubscriptions()
        .catch(err => {
            // Logic based on the err parameter
            return Observable.of(null);
        })
]);

This will just replace the error with null so you can handle it in the subscriber to the forkJoin.