一个 Rx observable 将充当 ReplaySubject 但仅适用于第一个订阅者？

Question

什么是构成类似于 ReplaySubject, but only emit the accumulated sequence once and for the first subscriber only (when that subscriber is connected)? After the 1st subscription, it should act just as a regular Subject.

的 Rx observable 的优雅方式

这是一个 .NET 项目，但我同样感谢 JavaScript/RxJS 个回答。

我为潜在的解决方案做了 google，我即将推出自己的解决方案，类似于 how I approached DistinctSubject，最终。

Answer 1

我稍微修改了中的实现，并将 class 的名称从 ReplayOnceSubject 更改为 ReplayFirstSubscriberOnlySubject:

public class ReplayFirstSubscriberOnlySubject<T> : ISubject<T>
{
    private readonly object _locker = new object();
    private ISubject<T> _subject = new ReplaySubject<T>();

    public void OnNext(T value) { lock (_locker) _subject.OnNext(value); }
    public void OnError(Exception error) { lock (_locker) _subject.OnError(error); }
    public void OnCompleted() { lock (_locker) _subject.OnCompleted(); }

    public IDisposable Subscribe(IObserver<T> observer)
    {
        if (observer == null) throw new ArgumentNullException(nameof(observer));
        lock (_locker)
        {
            if (_subject is ReplaySubject<T> replaySubject)
            {
                var subject = new Subject<T>();
                var subscription = subject.Subscribe(observer);
                // Now replay the buffered notifications
                replaySubject.Subscribe(subject).Dispose();
                replaySubject.Dispose();
                _subject = subject;
                return subscription;
            }
            else
                return _subject.Subscribe(observer);
        }
    }
}

这可能不是最有效的解决方案，因为每个操作都会获取两个不同的 lock（_locker 和 internal _gate），但是它应该也不会很差吧。

一个 Rx observable 将充当 ReplaySubject 但仅适用于第一个订阅者？

An Rx observable that would act as ReplaySubject but only for the 1st subscriber?

javascript

c#

reactive-programming

system.reactive

rxjs