错误：检测到无法访问的代码 ionic 3 天气应用

好的，所以我正在关注 ionic 3 上的遍历媒体教程，当我到达创建提供程序的部分时，我收到错误消息，指出在此处检测到无法访问的代码：

.map((res: Response) => res.json() );

它也在打字稿上说

找不到名称“地图”您的意思是“地图”吗？

import { HttpClient } from '@angular/common/http';
import { Injectable } from '@angular/core';
import 'rxjs/add/operator/map';

@Injectable()
export class WeatherProvider {
  apiKey = "89cca14f4ffcd27d602ad5e587f8e17f";
  url;

 constructor(public http: HttpClient) {
   console.log('Hello WeatherProvider Provider');
   this.url = "api.openweathermap.org/data/2.5/weather?q=";
 }



 getWeather(city, country){
 return this.http.get(this.url+city+','+country);
   .map((res: Response) => res.json() );
 }

}