Angular 无法在外部库中使用 HttpClient

## Angular 中外部库中使用 HttpClient 的问题与解决方案

typescript
import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs';
@Injectable({
  providedIn: 'root'
})
export class HttpService {
  constructor(private httpClient: HttpClient) { }
  getData(url: string): Observable {
    return this.httpClient.get(url);
  }
  // Other HTTP methods (post, put, delete) can also be implemented similarly
}

typescript
import { HttpService } from 'path-to-your-angular-service'; // Replace with the actual path
@Injectable()
export class ExternalLibraryService {
  constructor(private httpService: HttpService) { }
  fetchDataFromExternalAPI(): void {
    const apiUrl = 'https://api.example.com/data';
    
    this.httpService.getData(apiUrl).subscribe(
      (data) => {
        // Handle retrieved data from the external API
        console.log(data);
      },
      (error) => {
        // Handle errors
        console.error(error);
      }
    );
  }
}