如何从`rxjs` 包中正确导入操作符

问题描述

我很困惑如何导入这些运算符.有些我可以导入import 'rxjs/add/operator/do'; 还有一些我不能.例如，这不起作用:import 'rxjs/add/operator/map';(我检查了 rxjs/add/operator，map 存在于那里).

I am confused how to import those operators. Some I can import withimport 'rxjs/add/operator/do'; and some I can not. For ex, this does not work:import 'rxjs/add/operator/map'; (I checked in rxjs/add/operator, map exists there).

基本上我想做的是在 Angular4 中重现这个:

Essentially what I am trying to do is to reproduce this in Angular4:

var requestStream = Rx.Observable.just('https://api.github.com/users');

var responseStream = requestStream
  .flatMap(function(requestUrl) {
    return Rx.Observable.fromPromise(jQuery.getJSON(requestUrl));
  });

responseStream.subscribe(function(response) {
  // render `response` to the DOM however you wish
});

我也想知道如何处理just操作符，因为在rxjs/add/operator里看不到...

I also want to know how to deal with just operator, since I can not see it in rxjs/add/operator...

感谢您的帮助

推荐答案

RxJS 中有静态和实例操作符:

There are static and instance operators in RxJS:

static
   of
   interval

instance
   map
   first

你可能想像这样在 Observable 全局对象或 observable 实例上使用这些:

You may want to use these on the Observable global object or observable instance like this:

Observable.of()
observableInstance.map()

为此，您需要从 add 包中导入模块:

For that you need to import modules from the add package:

import 'rxjs/add/observable/of'
import 'rxjs/add/operator/map'

当你导入模块时，它本质上是通过添加与操作符对应的方法来修补 Observable 类或 Observable 原型.

When you import the module it essentially patches Observable class or Observable prototype by adding method corresponding to the operators.

但你也可以直接导入这些操作符，而不用修补Observable 或observableInstance:

But you can also import these operators directly and don't patch Observable or observableInstance:

import { of } from 'rxjs/observable/of';
import { map } from 'rxjs/operator/map';

of()
map.call(observableInstance)

随着 [email protected] 中可出租操作符的引入，您现在应该利用内置的 pipe 方法:

With the introduction of lettable operators in [email protected] you should now take advantage of the built-in pipe method:

import { of } from 'rxjs/observable/of';
import { map } from 'rxjs/operators/map';

of().pipe(map(), ...)

在RxJS:了解可出租运算符

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