处理未在动态对象上定义的C＃方法（又称为respond_to / method_missing）

问题描述

给定C＃4中的新动态支持，是否有可能以这样的方式编写一个类，如果一个方法被调用一个实例，并且该方法不存在，dispatch被传递到另一个方法？这可能类似：

  public class Apple：... {
 // ... 
 
 private ... MethodMissing（string name，...）{
 if（name ==TurnIntoOrange）{
 // do something 
} 
 } 
} 
 
 dynamic d = new Apple（）; 
 d.TurnIntoOrange（）; //实际上没有在苹果上定义;将传递给MethodMissing。 
  

其他语言在元编程的更通用标题下称为method_missing支持。我不知道什么C＃调用这个具体。但是有可能吗？

解决方案

当然。可以实施或衍生自用于更简单的路由。有关一些好的示例，请参见。

下面是 DynamicObject 的一个简单示例：

 使用系统; 
使用System.Dynamic; 
 
 public class MyDynamic：DynamicObject 
 {
 public override bool TryInvokeMember 
（InvokeMemberBinder binder，
 object [] args，
 out object result ）
 {
 Console.WriteLine（我将调用：{0}，
 binder.Name）; 
 result =dummy; 
 return true; 
} 
 
 public string NormalMethod（）
 {
 Console.WriteLine（In NormalMethod）; 
 returnnormal; 
} 
} 
 
 class Test 
 {
 static void Main（）
 {
 dynamic d = new MyDynamic ; 
 Console.WriteLine（d.HelloWorld（））; 
 Console.WriteLine（d.NormalMethod（））; 
} 
} 
  

plug>

我有一个更大的例子： DynamicObject ，但我尚未实现 IDyamicMetaObjectProvider 。我会在本书发布之前这样做，但是早期的访问版本目前只有 DynamicObject 示例。 Btw，如果你今天买它的一半价格 - 使用代码 twtr0711 。稍后我将编辑此答案以删除该位：）

< / plug>

Given the new dynamic support in C# 4, is it possible to write a class in such a way that if a method is invoked on an instance and that method is not present, dispatch is passed to another method? This might look something like:

public class Apple : ... {
  // ...

  private ... MethodMissing(string name, ...) {
    if (name == "TurnIntoOrange") {
      // do something
    }
  }
}

dynamic d = new Apple();
d.TurnIntoOrange();       // Not actually defined on Apple; will pass to MethodMissing.

Other languages would call this "method_missing support", under the more general heading of metaprogramming. I'm not sure what C# calls this specifically. But is it possible?

解决方案

Absolutely. Either implement IDynamicMetaObjectProvider or derive from DynamicObject for a much simpler route. See the DLR documentation for some good examples.

Here's a quick example of DynamicObject:

using System;
using System.Dynamic;

public class MyDynamic : DynamicObject
{
    public override bool TryInvokeMember
        (InvokeMemberBinder binder,
         object[] args,
         out object result)
    {
        Console.WriteLine("I would have invoked: {0}",
                          binder.Name);
        result = "dummy";
        return true;
    }

    public string NormalMethod()
    {
        Console.WriteLine("In NormalMethod");
        return "normal";
    }
}

class Test
{
    static void Main()
    {
        dynamic d = new MyDynamic();
        Console.WriteLine(d.HelloWorld());
        Console.WriteLine(d.NormalMethod());
    }
}

<plug>

I have a bigger example of DynamicObject in the 2nd edition of C# in Depth but I haven't yet implemented IDyamicMetaObjectProvider. I'll do so before the book's release, but the early access edition only has the DynamicObject example at the moment. Btw, if you buy it today it's half price - use the code twtr0711. I'll edit this answer later on to remove that bit :)

</plug>

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