Managing the rxjs from an Array of observables when the array has no elements

Looking for a more elegant solution to handle the case where an array of observables is empty in the following TypeScript function. I want the observable to complete when subscribe() is called without the need for an initial check.

I've already implemented a workaround using an if statement, but it's not ideal.

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

    return from(scan_operations).pipe(
            defaultIfEmpty([true]),
            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()),
        );
}

Answer №1

Using <code>from([]) will immediately conclude the observable, preventing subsequent operators from executing. There is no need to include length checking in this scenario.

 executeScanSessionUploads(scanOps: Array<Observable<any>>): Observable<any> {
        return from(scanOps).pipe(
                concatAll(),
                toArray(),
                switchMap((result) => this.sendDevices(result)),
                switchMap((result) => this.checkDeviceErrors(result)),
                tap(() => {
                    console.log('Scan Errors: ', this.scanErrors);
                }),
                tap(() => this.clearScanSessionData()),
            );

        }

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