rxjs 中的 Observable 和 Subject 有什么区别? [英] What is the difference between Observable and a Subject in rxjs?

问题描述

我正在浏览这个 博客 并阅读有关 Observables 的内容，但无法弄清楚Observable 和 Subject 的区别.

I was going through this blog and reading about Observables and couldn't figure out the difference between the Observable and a Subject.

推荐答案

在流编程中有两个主要接口:Observable 和 Observer.

In stream programming there are two main interfaces: Observable and Observer.

Observable是面向消费者的，可以转化和订阅:

Observable is for the consumer, it can be transformed and subscribed:

observable.map(x => ...).filter(x => ...).subscribe(x => ...)

Observer 是用于提供可观察源的接口:

Observer is the interface which is used to feed an observable source:

observer.next(newItem)

我们可以使用 Observer 创建新的 Observable:

We can create new Observable with an Observer:

var observable = Observable.create(observer => { 
    observer.next('first'); 
    observer.next('second'); 
    ... 
});
observable.map(x => ...).filter(x => ...).subscribe(x => ...)

或者，我们可以使用同时实现 Observable 和 Observer 接口的 Subject:

Or, we can use a Subject which implements both the Observable and the Observer interfaces:

var source = new Subject();
source.map(x => ...).filter(x => ...).subscribe(x => ...)
source.next('first')
source.next('second')

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