Rx.Subject 是一个热门的 observable 吗? [英] Is Rx.Subject a hot observable?

问题描述

代码

const a = new Rx.Subject().do(x => console.log('a'))
const b = a.mapTo(0)
const c = a.mapTo(1)
const d = Rx.Observable.merge(b, c)
d.subscribe(x => console.log('d'))
a.next(3)

和输出

a
d
a
d

为什么 a 会打印两次?Rx.Subject 不是一个热门的 observable 吗?

Why does a got printed twice? Isn't Rx.Subject a hot observable?

推荐答案

Subject 本身是热门/共享的.

The Subject itself is hot/shared.

但是:您附加的任何(大多数！)运算符都将创建一个新流，并将前一个流(在本例中为 Subject)作为源 - 新的然而，流(对于大多数操作符)并不热，只有通过附加 热操作符(如 share 或 publish 等等...)

However: Any(most!) operators that you append will create a new stream, with the previous stream(in this case the Subject) as source - the new stream, however, is (for most operators) not hot and will only be made hot by deriving a hot stream through appending a hot operator (like share or publish ect...)

所以当你share你的do时，一切都应该按预期进行.

So when you share your do, everything should work as expected.

const a = new Rx.Subject().do(x => console.log('a')).share();
const b = a.mapTo(0);
const c = a.mapTo(1);
const d = Rx.Observable.merge(b, c)
d.subscribe(x => console.log('d'));
a.next(3);

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