如何使一个可观察序列在发射之前先等待另一个完成? [英] How to make one Observable sequence wait for another to complete before emitting?

问题描述

说我有一个Observable，就像这样:

Say I have an Observable, like so:

var one = someObservable.take(1);

one.subscribe(function(){ /* do something */ });

然后，我还有第二个Observable:

var two = someOtherObservable.take(1);

现在，我想从subscribe()升级到two，但是我想确保在触发two订阅者之前，one已完成.

Now, I want to subscribe() to two, but I want to make sure that one has completed before the two subscriber is fired.

我可以在two上使用哪种缓冲方法来使第二个缓冲等待第一个缓冲完成?

What kind of buffering method can I use on two to make the second one wait for the first one to be completed?

我想我想暂停two直到one完成.

I suppose I am looking to pause two until one is complete.

推荐答案

我能想到的几种方法

import {take, publish} from 'rxjs/operators'
import {concat} from 'rxjs'

//Method one

var one = someObservable.pipe(take(1));
var two = someOtherObservable.pipe(take(1));
concat(one, two).subscribe(function() {/*do something */});

//Method two, if they need to be separate for some reason
var one = someObservable.pipe(take(1));
var two = someOtherObservable.pipe(take(1), publish());
two.subscribe(function(){/*do something */});
one.subscribe(function(){/*do something */}, null, two.connect.bind(two));

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