rxjs - Angular:如何等待一个可观察的函数，调用另一个返回可观察对象的函数？

import { Observable } from 'rxjs';
import { switchMap } from 'rxjs/operators';

// 可观察的函数1
function observableFunction1(): Observable<any> {
  return new Observable(observer => {
    // 模拟异步操作
    setTimeout(() => {
      observer.next('Observable 1 completed');
      observer.complete();
    }, 2000);
  });
}

// 可观察的函数2
function observableFunction2(): Observable<any> {
  return new Observable(observer => {
    // 模拟异步操作
    setTimeout(() => {
      observer.next('Observable 2 completed');
      observer.complete();
    }, 1000);
  });
}

// 等待可观察的函数1完成后调用可观察的函数2
observableFunction1().pipe(
  switchMap(() => observableFunction2())
).subscribe(result => {
  console.log(result);
});