创建一次性订阅 [英] Create one-time subscription

问题描述

我需要创建对 Observable 的订阅，该订阅在第一次调用时立即处理.

I need to create a subscription to an Observable that is immediately disposed of when it is first called.

有没有类似的东西:

observable.subscribeOnce(func);

我的用例，我在快速路由处理程序中创建订阅，并且每个请求都会多次调用订阅.

My use case, I am creating a subscription in an express route handler and the subscription is being called multiple times per request.

推荐答案

不能 100% 确定您需要什么，但如果您只想观察第一个值，则使用 first()或 take(1):

Not 100% certain about what you need, but if you only want to observe the first value, then use either first() or take(1):

observable.first().subscribe(func);

注意:.take(1) 和 .first() 都在满足条件时自动退订

note: .take(1) and .first() both unsubscribe automatically when their condition is met

来自编码员的评论.

import { first } from 'rxjs/operators'
    
observable
  .pipe(first())
  .subscribe(func);

原因

这篇关于创建一次性订阅的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！