如何在Angular中使用cache和update方法缓存API响应？

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable, of } from 'rxjs';
import { tap, shareReplay, switchMap } from 'rxjs/operators';

@Injectable({
  providedIn: 'root'
})
export class DataService {
  private cache$: Observable<any>;

  constructor(private http: HttpClient) {}

  getData(url: string): Observable<any> {
    if (!this.cache$) {
      this.cache$ = this.http.get(url).pipe(
        tap(() => console.log('Fetching data from API')),
        shareReplay(1)
      );
    }
    return this.cache$.pipe(
      switchMap(data => {
        // 模拟数据更新
        setTimeout(() => {
          this.updateData(url);
        }, 5000);
        return of(data);
      })
    );
  }

  private updateData(url: string): void {
    this.cache$ = this.http.get(url).pipe(
      tap(() => console.log('Updating data from API')),
      shareReplay(1)
    );
  }
}