错误:.map() 不是函数 [英] Error : .map() is not a function

问题描述

尝试订阅已解析的 HTTP 响应 - 来自组件的 GET.得到一个错误，说 .map 不是从 HTTPService 或组件类使用的函数.

Trying to subscribe to the parsed response of HTTP - GET from the component. Getting a error saying .map is not a function whether used from HTTPService or from the component class.

Httpdemo.getResponse().map(res => res.json()).subscribe((cities)=>{ 
   this.cities = cities.cities;          
   console.log(this.cities);
});

但以下工作:

Httpdemo.getResponse().subscribe((cities)=>{ 
    this.cities = JSON.parse(cities._body).cities;          
    console.log(this.cities);
});

解析在 Httpdemo 服务中也不起作用.

The parsing also does not work in the Httpdemo service.

return this.http.get('./app/cities.json').map(res => res.json())

我的代码中这里的用法有什么问题?

What is wrong with the usage here in my code?

推荐答案

您需要为 Observable 导入 map 操作符，如下所述:

You need to import the map operator for Observable as described below:

import 'rxjs/add/operator/map';

默认情况下，并非所有运算符都包括在内.

By default not all operators are included.

查看此答案了解更多详情:

See this answer for more details:

• Angular 2 HTTP GET with TypeScript 错误 http.get(...).map is not a function in [null]

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