似乎无法在Observable上使用"first()"(Angular中的rxjs) [英] can't seem to use 'first()' on Observable(rxjs in Angular)

问题描述

我了解了RXJS中的这一出色功能，从理论上讲，它仅允许我订阅一个响应，但似乎无法实现.相反，我收到此错误，

I read about this awesome feature in RXJS which would theoretically allow me to subscribe only for one response, but can't seem to implement it. Instead, I'm getting this error,

属性第一"在可观察"类型上不存在."

"Property 'first' does not exist on type 'Observable'."

尽管我只是从现有示例中复制粘贴.这是我的代码:

although I am just copy-pasting from existing examples. Here's my code:

implementHash( token ){
    console.log('trying to implement hash', token);
    const req = this.http.get('http://localhost:3003/token/' + token );
    const sub = req
        //.first()
        .subscribe( res =>{
            sub.unsubscribe; // trying to avoid this line
    });
};

推荐答案

您需要

import'rxjs/add/operator/first';

在您的文件中.

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