如何在Angular9中使用Promise.all进行两次api调用？

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';

@Injectable({
  providedIn: 'root'
})
export class ApiService {
  constructor(private http: HttpClient) { }

  getFirstData(): Promise<any> {
    return this.http.get('api/first').toPromise();
  }

  getSecondData(): Promise<any> {
    return this.http.get('api/second').toPromise();
  }
}

import { Component, OnInit } from '@angular/core';
import { ApiService } from './api.service';

@Component({
  selector: 'app-root',
  template: `
    <div>
      <p>First API Result: {{ firstData }}</p>
      <p>Second API Result: {{ secondData }}</p>
    </div>
  `,
})
export class AppComponent implements OnInit {
  firstData: any;
  secondData: any;

  constructor(private apiService: ApiService) { }

  ngOnInit() {
    Promise.all([this.apiService.getFirstData(), this.apiService.getSecondData()])
      .then(([firstData, secondData]) => {
        this.firstData = firstData;
        this.secondData = secondData;
      })
      .catch(error => {
        console.error('Error:', error);
      });
  }
}