[英]How do I turn a polling system into an Rx.Net IObservable?
I have a game (based on MonoGame / XNA) with an update method like so: 我有一个游戏(基于MonoGame / XNA)和更新方法,如下所示:
public void Update(GameTime gameTime)
{
component.Update(gameTime);
}
I would like to convert this to the Reactive pattern. 我想将其转换为Reactive模式。 My current solution is:
我目前的解决方案是:
public void Initialize()
{
updateSubject = new Subject<GameTime>();
component = new Component();
updateSubject.Subscribe((gameTime) => component.Update(gameTime));
}
public void Update(GameTime gameTime)
{
updateSubject.OnNext(gameTime);
}
I am new to Rx so I am still learning the best way of doing things. 我是Rx的新手,所以我仍然在学习最好的做事方式。 I read that
Subject
should be avoided and Observable.Create
should be used instead. 我读到应该避免使用
Subject
而应该使用Observable.Create
。
Is Subject
appropriate here? 这里的
Subject
是否合适?
How could I use Observable.Create
in this case? 在这种情况下我怎么能使用
Observable.Create
?
The key issue you're facing here is that you need a source for your observable. 您在这里遇到的关键问题是您需要一个可观察源。 In general you can create observables from a variety of sources from events, delegates, tasks, many of the observable extensions (like
.Interval
or .Generate
), and subjects. 通常,您可以从事件,委托,任务,许多可观察扩展(如
.Interval
或.Generate
)和主题等各种来源创建可观察对象。
In your case you must have a source that you can have code, external to your observable, push values to. 在您的情况下,您必须拥有一个源代码,您可以拥有代码,在您的observable外部,将值推送到。 In this case a subject is perfectly fine, but you could just use a delegate also.
在这种情况下,主题完全没问题,但您也可以使用代理。
If you use a subject then your code is fine. 如果您使用主题,那么您的代码就可以了。 The only downside is that you could call
updateSubject.OnCompleted
and finish the observable. 唯一的缺点是你可以调用
updateSubject.OnCompleted
并完成observable。
If you want to use a delegate then your code could look like this: 如果您想使用委托,那么您的代码可能如下所示:
private Action<GameTime> updateGameTime = null;
public void Initialize()
{
component = new Component();
Observable
.FromEvent<GameTime>(a => updateGameTime += a, a => updateGameTime -= a)
.Subscribe((gameTime) => component.Update(gameTime));
}
public void Update(GameTime gameTime)
{
updateGameTime(gameTime);
}
In this way the only thing you can do with updateGameTime
is pass in a new GameTime
- you can't "accidentally" end the sequence. 通过这种方式,你可以用
updateGameTime
做的唯一事情是传入一个新的GameTime
- 你不能“意外地”结束序列。
Now the whole issue with using subjects versus Observable.Create
is one of state. 现在使用主题与
Observable.Create
的整个问题是状态之一。 In your code you need state, so a subject is OK. 在您的代码中,您需要状态,因此主题是可以的。 In general though, and whenever possible, it is advisable to encapsulate state - and that's what
Observable.Create
does for you. 通常,尽管如此,建议封装状态 - 这就是
Observable.Create
为您所做的事情。
Take this example: 举个例子:
var i = -1;
var query =
Observable
.Range(0, 10).Select(x =>
{
i = -i * 2;
return x * i;
});
If I subscribe to this observable twice I get these two sequences: 如果我订阅这个可观察的两次,我得到这两个序列:
(1) (1)
0 -4 16 -48 128 -320 768 -1792 4096 -9216
(2) (2)
0 -4096 16384 -49152 131072 -327680 786432 -1835008 4194304 -9437184
The sequence changes because I used state (ie var i = -1;
). 序列发生变化,因为我使用了状态(即
var i = -1;
)。
Had I written the code with Observable.Create
I could avoid this state: 如果我用
Observable.Create
编写代码,我可以避免这种状态:
var query =
Observable
.Create<int>(o =>
{
var i = -1;
return
Observable
.Range(0, 10).Select(x =>
{
i = -i * 2;
return x * i;
})
.Subscribe(o);
});
It is still the same query, but the state is encapsulated, so if I subscribe twice now I get: 它仍然是相同的查询,但状态是封装的,所以如果我现在订阅两次,我得到:
(1) (1)
0 -4 16 -48 128 -320 768 -1792 4096 -9216
(2) (2)
0 -4 16 -48 128 -320 768 -1792 4096 -9216
There are times when writing complex queries that you might think that using a subject would make it much easier, and in general, that's where mistakes occur. 有时编写复杂的查询时,您可能会认为使用主题会使其变得更容易,而且通常情况下,这就是错误发生的地方。 You should always try to find a pure operator approach before using subjects in this case.
在这种情况下,在使用主题之前,您应该总是尝试找到纯运算符方法。 If you can't then encapsulate the use of a subject in
Observable.Create
. 如果你不能在
Observable.Create
封装主题的使用。
It's times like yours that using a subject is fine because you need that external state. 像你这样的时候使用主题很好,因为你需要那个外部状态。
Just pointing out that you code unnessecarily uses Rx. 只是指出你代码unnessecarily使用Rx。
public void Initialize()
{
//updateSubject = new Subject<GameTime>();
component = new Component();
//updateSubject.Subscribe((gameTime) => component.Update(gameTime));
}
public void Update(GameTime gameTime)
{
//updateSubject.OnNext(gameTime);
component.Update(gameTime)
}
Here I have removed the Subject
and just call directly through to the component
s Update
method, to illustrate the point. 在这里,我删除了
Subject
并直接调用component
的Update
方法,以说明这一点。
Perhaps you are looking for a private method of polling? 也许你正在寻找私人投票方法? In which case
Observable.Interval
could be a good place to start. 在这种情况下,
Observable.Interval
可能是一个很好的起点。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.