Rxjs:Observable.First 与 Single 与 Filter 之间的区别 [英] Rxjs: Difference between Observable.First vs Single vs Filter

问题描述

我正在探索 RxJS 库，并且非常喜欢使用 Observable 而不是 Promise.但是，有人可以提供有关使用

I am exploring RxJS library and really a fan of using Observable instead of Promise. However, can someone provide any detailed information about the difference between using

• Observable.First
• Observable.Single
• 以只返回单个项目的方式应用过滤器

这个库中对于 Single 的具体需求是什么?

What is the need for Single specifically in this library?

推荐答案

如果过滤器的意思是:

let emitted = false;
obs = obs.filter(x => {
  if(emitted) {
    return false;
  } else {
    emitted = true;
    return true;
  }
});

过滤器(在这种特殊情况下，检查上面的代码)

Filter (in this particular case, check the code above)

会在第一项出现后立即发出.将忽略所有后续项目.将在源 observable 完成时完成.

Will emit as soon as first item appears. Will ignore all subsequent items. Will complete when source observable completes.

in : -1-2-3--|---
out: -1------|---

第一

会在第一项出现后立即发出.之后将完成.

Will emit as soon as first item appears. Will complete right after that.

in : -1-2-3--|---
out: -1|----------

单人

如果源 observable 发出多个事件将失败.

Will fail if source observable emits several events.

in : -1-2-3--|---
out: -1-X---------

将在源可观察完成时发出(并且 single 可以确保不会再发出任何内容).之后将完成.

Will emit when source observable completes (and single can be sure nothing more can be emitted). Will complete right after that.

in : -1------|---
out: --------1|--

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