[RxJS] Subject basic

最新推荐文章于 2025-07-06 13:00:46 发布

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最新推荐文章于 2025-07-06 13:00:46 发布

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原文链接：http://www.cnblogs.com/Answer1215/p/5774175.html

本文探讨了ASubject在Reactive Extensions中扮演的角色：既是Observer又是Observable。通过示例展示了如何作为Observable发送消息，以及如何作为Observer接收来自其他Observables的数据。

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A Subject is a type that implements both Observer and Observable types. As an Observer, it can subscribe to Observables, and as an Observable it can produce values and have Observersw subscribe it.

First time I read

implements both Observer and Observable types

I was quite confused.

As a Observable:

var subject = new Rx.Subject();
var subscription = subject.subscribe(
   function onNext(x) { console.log('onNext: ' + x); },
   function onError(e) { console.log('onError: ' + e.message); },
   function onCompleted() { console.log('onCompleted'); }
);
subject.onNext('Our message #1');
subject.onNext('Our message #2');

/*
"onNext: Our message #1"
"onNext: Our message #2"
*/

Every time we call onNext() message to yield the value.

As a Observer, so we use 'source' to sebscribe 'subject', then subscribe 'subject' again to get the side effect

var subject = new Rx.Subject();
var source = Rx.Observable.interval(300)
   .map(function(v) { return 'Interval message #' + v; })
   .take(5);
source.subscribe(subject);
var subscription = subject.subscribe(
   function onNext(x) { console.log('onNext: ' + x); },
   function onError(e) { console.log('onError: ' + e.message); },
   function onCompleted() { console.log('onCompleted'); }
);
setTimeout(function() {
   subject.onCompleted();
}, 1000);

/*
"onNext: Interval message #0"
"onNext: Interval message #1"
"onNext: Interval message #2"
"onCompleted"
*/