如何使一个可观察序列在发射之前先等待另一个完成?
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.
答
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));