CODEWITHSUNDEEP
typescriptrxjs
Martin
Martin

Reputation: 441

Handle rxjs from(Array<observables>) when the array is empty

Given the following function, in typescript, that returns an observable and receives an Array of Observables, how can I, in a more elegant way, remove the first if, that checks if the array is empty, in order for the observable to complete, when called subscribe() on the function.

I implemented the if. But it looks ugly. 

perform_scan_session_uploads(scan_operations: Array<Observable<any>>): Observable<any> {
        // TODO: Check the errors in this inner observable.

        if (scan_operations.length === 0) {
            return of([true]);
        }

    return from(scan_operations).pipe(
            concatAll(),
            toArray(),
            switchMap((result) => this.send_devices(result)),
            switchMap((result) => this.check_device_errors(result)),
            tap(() => {
                console.log('Scan Errors: ', this.scan_errors);
            }),
            tap(() => this.clean_scan_session_data()),
        );

    }

Upvotes: 0

Views: 407

Answers (1)

Fan Cheung
Fan Cheung

Reputation: 11345

from([]) will immediately completes the observable so the subsequent operators won't execute. it's fine to skip the length checking

 perform_scan_session_uploads(scan_operations: Array<Observable<any>>): Observable<any> {
        return from(scan_operations).pipe(
                concatAll(),
                toArray(),
                switchMap((result) => this.send_devices(result)),
                switchMap((result) => this.check_device_errors(result)),
                tap(() => {
                    console.log('Scan Errors: ', this.scan_errors);
                }),
                tap(() => this.clean_scan_session_data()),
            );

        }

Upvotes: 1

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