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  • [rxjs] Shares a single subscription -- publish()

    If have an observable and you subscribe it twice, those tow subscritions have no connection. 

    console.clear();
    var Observable = Rx.Observable;
    var _id = 1;
    
    var source = Observable.create(function(Observe){
      var myId = _id++;
      Observe.onNext('Observable ' + myId);
      setTimeout(function(){
        Observe.onNext('Observable... ' + myId);
        Observe.onCompleted();
      }, 1000);
    });
    
    var subscrition1 = source.subscribe(function onNext(x){
      console.log('Observable 1: ' + x);
    });
    
    var subscrition2 = source.subscribe(function onNext(x){
      console.log('Observable 2: ' + x);
    });

    Result:

    /*"Observable 1: Observable 1"
    "Observable 2: Observable 2"
    "Observable 1: Observable... 1"
    "Observable 2: Observable... 2"*/

    publish():

    Returns an observable sequence that is the result of invoking the selector on a connectable observable sequence that shares a single subscription to the underlying sequence.

    console.clear();
    var Observable = Rx.Observable;
    var _id = 1;
    
    var source = Observable.create(function(Observe){
      var myId = _id++;
      Observe.onNext('Observable ' + myId);
      setTimeout(function(){
        Observe.onNext('Observable... ' + myId);
        Observe.onCompleted();
      }, 1000);
    });
    var published = source.publish();
    
    var subscrition1 = published.subscribe(function onNext(x){
      console.log('Observable 1: ' + x);
    });
    
    var subscrition2 = published.subscribe(function onNext(x){
      console.log('Observable 2: ' + x);
    });
    
    var connection = published.connect();

    Results:

    /*
    "Observable 1: Observable 1"
    "Observable 2: Observable 1"
    "Observable 1: Observable... 1"
    "Observable 2: Observable... 1"
    */

    You can see the result just have one single subscrition then.

    You can dispose the connection:

    connection.dispose();

    Results:

    /*"Observable 1: Observable 1"
    "Observable 2: Observable 1"*/

    There is a problem when you connect the published observables at different place.

    var Observable = Rx.Observable;
    var _id = 1;
    
    var source = Observable.create(function(Observe){
      var myId = _id++;
      Observe.onNext('Observable ' + myId);
      setTimeout(function(){
        Observe.onNext('Observable... ' + myId);
        Observe.onCompleted();
      }, 1000);
    });
    var published = source.publish();
    var connection = published.connect();
    
    var subscrition1 = published.subscribe(function onNext(x){
      console.log('Observable 1: ' + x);
    });
    
    var subscrition2 = published.subscribe(function onNext(x){
      console.log('Observable 2: ' + x);
    });
    
    //var connection = published.connect();

    Results:

    /*"Observable 1: Observable... 1"
    "Observable 2: Observable... 1"*/

    If we move the connect() funciton up before subscribe(). Then we missed the very first console.log(); It means connection is already start, but no one subscribe it yet.

    Therefore, we don't use publish() funciton alone, more than often we use publish().refCount() function together.

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  • 原文地址:https://www.cnblogs.com/Answer1215/p/4754960.html
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