Angular嵌套订阅代码未按预期工作

import { Component, OnDestroy } from '@angular/core';
import { Observable, Subject } from 'rxjs';
import { switchMap, takeUntil } from 'rxjs/operators';

@Component({
  selector: 'app-example',
  template: '...'
})
export class ExampleComponent implements OnDestroy {
  private destroy$ = new Subject<void>();

  ngOnDestroy() {
    this.destroy$.next();
    this.destroy$.complete();
  }

  outerObservable$: Observable<any>;
  innerObservable$: Observable<any>;

  loadData() {
    this.outerObservable$.pipe(
      switchMap(outerValue => {
        // 根据外部Observable的值获取内部Observable
        return this.innerObservable$.pipe(
          takeUntil(this.destroy$) // 在组件销毁时取消订阅内部Observable
        );
      }),
      takeUntil(this.destroy$) // 在组件销毁时取消订阅外部Observable
    ).subscribe(
      result => {
        // 处理订阅结果
      },
      error => {
        // 处理错误情况
      }
    );
  }
}