当数组为空时处理来自(Array<observables>) 的 rxjs

Question

给定以下函数，在 typescript 中，它返回一个 observable 并接收一个 Observable 数组，我怎样才能以更优雅的方式删除第一个 if，它检查数组是否为空，以便 observable在函数上调用 subscribe() 时完成。

我实现了 if。但它看起来很丑。

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()),
        );

    }

Answer 1

from([]) 将立即完成 observable，因此后续运算符不会执行。可以跳过长度检查

 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()),
            );

        }