在angular 2中api调用失败时如何捕获错误

import { HttpClient, HttpErrorResponse } from '@angular/common/http';
import { Observable, throwError } from 'rxjs';
import { catchError } from 'rxjs/operators';

// ...

constructor(private http: HttpClient) { }

// ...

makeApiCall(): Observable<any> {
  return this.http.get('api-url').pipe(
    catchError(this.handleError)
  );
}

private handleError(error: HttpErrorResponse) {
  if (error.error instanceof ErrorEvent) {
    // 客户端错误，例如网络连接问题
    console.error('An error occurred:', error.error.message);
  } else {
    // 服务器返回错误响应
    console.error(
      `Backend returned code ${error.status}, ` +
      `body was: ${error.error}`);
  }
  // 返回一个带有错误信息的可观察对象
  return throwError('Something bad happened; please try again later.');
}

this.makeApiCall().subscribe(
  response => {
    // 处理API成功响应的逻辑
  },
  error => {
    // 处理API调用失败的逻辑
  }
);