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  • 001.Reactive Extensions

    基本概念

    The Reactive Extensions (Rx) is a library for composing asynchronous and event-based programs using observable sequences and LINQ-style query operators.

    Reactive Extensions represents all these data sequences as observable sequences. An application can subscribe to these observable sequences to receive asynchronous notifications as new data arrive.

    Push-based/Pull-based

    Rx的主要的接口

    IObservable<T>/IObserver<T>

    IObservable<T>就是observable sequences 的抽象,就像Pull-based中的IEnumerable<T>类似,用来承载数据,代表了一个可以被观察的数据源,他可以在将sequences中的数据,推送给任何一个有兴趣的listener,我们用IObserver<T>来代表这种对IObservable<T>感兴趣的listener。

    一个IObservable<T>的实现可以被视为一个T类型数据的集合, 例如IObservable<int>可以被视为一个int类型数据的集合,他们会被推送给IObserver<T>这样的订阅者。
    我们看一下接口的定义:

    1. public interface IObservable<out T>
    2. {
    3. IDisposable Subscribe(IObserver<T> observer);
    4. }
    5. public interface IObserver<in T>
    6. {
    7. void OnCompleted(); // Notifies the observer that the source has finished sending messages.
    8. void OnError(Exception error); // Notifies the observer about any exception or error.
    9. void OnNext(T value); // Pushes the next data value from the source to the observer.
    10. }

    Rx还通过扩展的方式提供了一些订阅更方便的方式,不需要实现自己的IObserver<T>,只需要实现对应的订阅事件(OnNext, OnError, OnComplete)对应的delegate方法即可,如下面的例子:

    1. IObservable<int> source = Observable.Range(1, 5); //creates an observable sequence of 5 integers, starting from 1
    2. IDisposable subscription = source.Subscribe(
    3. x => Console.WriteLine("OnNext: {0}", x), //prints out the value being pushed
    4. ex => Console.WriteLine("OnError: {0}", ex.Message),
    5. () => Console.WriteLine("OnCompleted"));

    上面这只是两个例子,在实际的开发应用中,我没几乎没有必要自己去实现这两个接口,Rx通过ObservableObserver为我们提供了丰富的足够的实现,后面将继续说明。





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  • 原文地址:https://www.cnblogs.com/boulder/p/6657745.html
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