zoukankan      html  css  js  c++  java
  • [RxJS] Reusable multicasting with Subject factories

    The way we use publish() (or multicast with an RxJS Subject) makes the shared Observable not reusable if the shared execution happens to complete or emit an error. In this lesson we will see how to use a simple Subject factory function in order to create a new Subject, one for each shared execution, whenever connect() is called.

    var shared = Rx.Observable.interval(1000).take(3)
      .do(x => console.log('source ' + x))
      .multicast(new Rx.Subject())
      .refCount();

    The code above, after subject emit 0,1,2, three values, then it completes. It means if you want to subscribe the subject again, it won't emit anything because it is completed. 

    If you want to reuse the 'shared' subject even after subject complete, you need to use subject factories, which simply just a function return new Subject():

    function subjectFactory() {
      return new Rx.Subject(); 
    }
    
    var shared = Rx.Observable.interval(1000).take(3)
      .do(x => console.log('source ' + x))
      .multicast(subjectFactory)
      .refCount();

    So now even you resubscribe after subject complete, it will emit you new value.

    function subjectFactory() {
      return new Rx.Subject(); 
    }
    
    var shared = Rx.Observable.interval(1000).take(3)
      .do(x => console.log('source ' + x))
      .multicast(subjectFactory)
      .refCount();
    
    // subject: --0--1--2--3--4--5|
    //                               A
    // subject2:                     --0--1--2--3--4--5|
    
    var observerA = {
      next: function (x) { console.log('A next ' + x); },
      error: function (err) { console.log('A error ' + err); },
      complete: function () { console.log('A done'); },
    };
    
    var subA = shared.subscribe(observerA); // 0 => 1
    console.log('subscribed A');
    
    var observerB = {
      next: function (x) { console.log('B next ' + x); },
      error: function (err) { console.log('B error ' + err); },
      complete: function () { console.log('B done'); },
    };
    
    var subB;
    setTimeout(function () {
      subB = shared.subscribe(observerB);
      console.log('subscribed B');
    }, 2000);
    
    setTimeout(function () {
      subA.unsubscribe();
      console.log('unsubscribed A');
    }, 3000);
    
    setTimeout(function () {
      subB.unsubscribe();
      console.log('unsubscribed B');
    }, 5000);
    
    setTimeout(function () {
      subA = shared.subscribe(observerA); // 0 => 1 (connect)
      console.log('subscribed A');
    }, 6000);
    /**
    "subscribed A"
    "source 0"
    "A next 0"
    "source 1"
    "A next 1"
    "subscribed B"
    "source 2"
    "A next 2"
    "B next 2"
    "A done"
    "B done"
    "unsubscribed A"
    "unsubscribed B"
    "subscribed A"
    "source 0"
    "A next 0"
    "source 1"
    "A next 1"
    "source 2"
    "A next 2"
    "A done"
    
    */
  • 相关阅读:
    多态与鸭子类型
    mixin与派生
    4.9作业
    property
    继承
    封装
    《梦断代码》阅读笔记1
    阅读笔记3——《大道至简》第四、五、六章
    阅读笔记2——《大道至简》第二、三章
    阅读笔记1——《大道至简》第一章
  • 原文地址:https://www.cnblogs.com/Answer1215/p/6001403.html
Copyright © 2011-2022 走看看