UniRx_UniTask_学习记录_2.3_Observable的性质

2.3 Observable 的性质

• 由不同方法和时机生成的Observable 各有不同， 什么时候运作，如何运作。我们需要对这些有明确的了解

2.3.1 Observable 行动时机

• 声明Observable时，出入停止的状态，当跟各种 Operator进行连，并Subscribe()后才开始处理内部消息的传达

• Observable 的构成和连接流程

• 

• Subscribe() 的时机 和 动作

  • 再Subscribe()后，Operator才会接受消息

    using UniRx;
    var subject = new Subject<string>();
    // OnNext 的内容用空格隔开。最后再输出
    var appendStringObservable =
    subject
    .Scan((previous, current) => previous + " " + current)
    .Last();
    // Subscribe（这时 Observable 开始运作）
    appendStringObservable.Subscribe(x => Debug.Log(x));
    subject.OnNext("I");
    subject.OnNext("have");
    subject.OnNext("a");
    subject.OnNext("pen.");
    subject.OnCompleted();
    subject.Dispose();
    
    /*
    	结果
    	I have a pen.
    */
    

    using UniRx;
    var subject = new Subject<string>();
    // OnNext 的内容用空格隔开。最后再输出
    var appendStringObservable =
    subject
    .Scan((previous, current) => previous + " " + current)
    .Last();
    // Subscribe 前 发行消息
    subject.OnNext("I");
    subject.OnNext("have");
    // 途中 Subscribe 
    appendStringObservable.Subscribe(x => Debug.Log(x));
    subject.OnNext("a");
    subject.OnNext("pen.");
    subject.OnCompleted();
    subject.Dispose();
    /*
    	结果
    	a pen.
    */
    

  • 不会处理 Subscribe() 之前发行的消息

2.3.2 Operator 的 实例化生成

// using UniRx;
var subject = new Subject<int>();

var observable = subject.Do(x => Debug.Log("Do:" + x));
// 订阅两次 Subscribe 
observable.Subscribe(x => Debug.Log("First subscribe:" + x));
observable.Subscribe(x => Debug.Log("Second subscribe:" + x));
subject.OnNext(1);
subject.OnCompleted();
subject.Dispose();

/*
Do:1
First subscribe:1
Do:1
Second subscribe:1
*/

2.3.3 Hot Observable 和 Cold Observable

Cold Observable 是 谁都没有订阅处于停止状态的Observable，Hot Observable 则是已经再运作的Observable

Operator 基本上是Cold Observable

• Hot 变换

  • 使用Subject

    using UniRx;
    var originalSubject = new Subject<string>();
    // OnNext 的内容用空格隔开。最后再输出
    var appendStringObservable =
    originalSubject
    .Scan((previous, current) => previous + " " + current)
    .Last();
    
    // Subject
    var publishSubject = new Subject<string>();
    
    // 这个时候 appendStringObservable 开始运作
    appendStringObservable.Subscribe(publishSubject);
    originalSubject.OnNext("I");
    originalSubject.OnNext("have");
    
    // 途中 publishSubject 进行Subscribe
    publishSubject.Subscribe(x => Debug.Log(x));
    originalSubject.OnNext("a");
    originalSubject.OnNext("pen.");
    originalSubject.OnCompleted();
    // 解除 Hot 変換
    publishSubject.Dispose();
    originalSubject.Dispose();
    
    /*
    I have a pen.
    */
    

    这样可以防止Operator 漏接消息

  • 代替Subject 的专用 Operator

    // using UniRx;
    var originalSubject = new Subject<string>();
    
    // IConnectableObservable<string>
    IConnectableObservable<string> appendStringObservable =
    originalSubject
    .Scan((previous, current) => previous + " " + current)
    .Last()
    .Publish(); // Hot 变化的 Operator
    // IConnectableObservable.Connect() 内部的Subscribe开始执行
    var disposable = appendStringObservable.Connect();
    originalSubject.OnNext("I");
    originalSubject.OnNext("have");
    // appendStringObservable 直接Subscribe 
    appendStringObservable.Subscribe(x => Debug.Log(x));
    originalSubject.OnNext("a");
    originalSubject.OnNext("pen.");
    originalSubject.OnCompleted();
    // 解除Hot变换 
    disposable.Dispose();
    originalSubject.Dispose();
    

    还有很多别的变换用Operator

• Hot变换的好处

  • 所有的Operator 都处于运作状态并接受和床底消息

  • 共有运作中的Operator，不用每次都生成新的