如何在angular 7中管理多个可观察对象

import { Observable, forkJoin, combineLatest } from 'rxjs';
import { map, switchMap } from 'rxjs/operators';

const observable1 = new Observable(observer => {
  observer.next('Observable 1');
});

const observable2 = new Observable(observer => {
  observer.next('Observable 2');
});

const observable3 = new Observable(observer => {
  observer.next('Observable 3');
});

forkJoin([observable1, observable2, observable3]).subscribe(results => {
  console.log(results); // ['Observable 1', 'Observable 2', 'Observable 3']
});

combineLatest([observable1, observable2, observable3]).subscribe(results => {
  console.log(results); // ['Observable 1', 'Observable 2', 'Observable 3']
});

observable1.pipe(
  switchMap(result1 => {
    // 根据observable1的结果处理其他可观察对象
    return observable2;
  })
).subscribe(result2 => {
  console.log(result2); // 'Observable 2'
});