单独召集代表？ [英] Calling delegates individually?

问题描述

如果我有一个这样的代表：

if I have a delegate like so:

 Delegate void Render();
 Render ToRender;

并在此使用：

 ToRender += FunctionRender;
 ToRender += SomeOtherRender;

如何使它能够单独调用每个功能？这样做：

How can I make it so I can invoke each function seperately? Something like this:

 foreach(Render render in ToRender)
 {
     BeginRender();


     render();


     EndRender();
 }

推荐答案

您可以分别获取每个使用 Delegate.GetInvocationList（） 。

You can fetch each one separately using Delegate.GetInvocationList().

foreach (Render render in ToRender.GetInvocationList())
{
    ...
}

请注意， GetInvocationList ）只返回一个 Delegate [] ，但 foreach 在每个项目上都有一个隐式转换，这是什么使上述循环工作。

Note that GetInvocationList() just returns a Delegate[], but foreach has an implicit cast on each item, which is what makes the above loop work.

哦，你应该检查是否 ToRender 是 null 或者不是第一，当然 - 否则你会得到一个 NullReferenceException 。你可以写一个通用的扩展方法来使这个更好，但是你需要对C＃中不允许的委托类型有一个限制：（

Oh, and you should check whether ToRender is null or not first, of course - otherwise you'll get a NullReferenceException. You could actually write a generic extension method to make this nicer, but you'd need a constraint on the delegate type which isn't allowed in C# :(

如果你不要在乎缺乏限制，你可以伪造它：

If you don't care about the lack of constraints, you could fake it:

public static IEnumerable<T> GetIndividualDelegates<T>(this T multiDelegate)
    where T : class
{
    if (multiDelegate == null)
    {
        yield break;
    }
    Delegate d = (Delegate)(object) multiDelegate;
    foreach (Delegate item in d.GetInvocationList())
    {
         yield return (T)(object) item;
    }    
}

（由于通用转化的限制，这很尴尬。）

(It's awkward because of the restrictions on generic conversions.)

这样你可以写：

foreach (Render render in ToRender.GetIndividualDelegates())
{
    ...
}

不用担心是否 T oRender 为空。

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