可观察类属性不触发订阅

Question

简单的可观察变量按预期工作，并在同一线程上立即触发回调。为什么任何可观察类型的类变量(Subject、ISubject、observable、IOobservable(都不会触发回调？

带有简单变量的示例-[Works]

var x1 = new Subject<string>();
var x2 = x1.DistinctUntilChanged();
x2.Subscribe(o =>
{
// Triggered as expected
});
x1.OnNext("Hello");

类的示例-[不工作]

public class InstrumentModel
{
public Subject<string> Demo => new Subject<string>();
}
var class1 = new InstrumentModel();
class1.Demo
//.DistinctUntilChanged()
//.SubscribeOn(Scheduler.CurrentThread)
//.ObserveOn(Scheduler.CurrentThread)
.Subscribe(o =>
{
// Never triggered 
});
class1.Demo.OnNext("Hello");

Answer 1

问题是您使Demo在每次使用时都返回Subject<string>的新实例。

您也订阅的Demo实例与您在.上调用的OnNext()实例不同

class1.Demo.Subscribe(...); // makes new instance `Subject<string>`
class1.Demo.OnNext("Hello"); // makes another new instance of `Subject<string>`

保持它的实例不变，它就会工作。例如：

public class InstrumentModel
{
public Subject<string> Demo = new Subject<string>();
}

或：

public class InstrumentModel
{
public InstrumentModel()
{
this.Demo = new Subject<string>();
}
public Subject<string> Demo { get; }
}