枚举类型的命名空间 - 最佳做法 [英] namespaces for enum types - best practices

问题描述

通常，一个人需要几个枚举类型。有时，有一个名字冲突。这两个解决方案可以想到：使用命名空间，或使用'较大'枚举元素名称。仍然，命名空间解决方案有两个可能的实现：一个带有嵌套枚举的虚拟类或一个完整的命名空间。

我正在寻找所有三种方法的利弊

示例：

  //看到手工制作的名称冲突解决方案
枚举eColors {cRed，cColorBlue，cGreen，cYellow，cColorsEnd}; 
 enum eFeelings {cAngry，cFeelingBlue，cHappy，cFeelingsEnd}; 
 void setPenColor（const eColors c）{
 switch（c）{
 default：assert（false）; 
 break; case cRed：// ... 
 break; case cColorBlue：// ... 
 // ... 
} 
} 
 
 
 //（ab）使用一个类作为命名空间
 class Colors {enum e {cRed，cBlue，cGreen，cYellow，cEnd}; }; 
 class Feelings {enum e {cAngry，cBlue，cHappy，cEnd}; }; 
 void setPenColor（const Colors :: e c）{
 switch（c）{
 default：assert（false）; 
 break; case Colors :: cRed：// ... 
 break; case Colors :: cBlue：// ... 
 // ... 
} 
} 
 
 
 //一个真正的命名空间？ 
命名空间颜色{enum e {cRed，cBlue，cGreen，cYellow，cEnd}; }; 
命名空间感觉{enum e {cAngry，cBlue，cHappy，cEnd}; }; 
 void setPenColor（const Colors :: e c）{
 switch（c）{
 default：assert（false）; 
 break; case Colors :: cRed：// ... 
 break; case颜色:: cBlue：// ... 
 // ... 
} 
} 
  

解决方案

命名空间（ class ）是您可以使用使用声明。

使用命名空间的问题是，可以在代码的其他位置扩展命名空间。在一个大型项目中，不能保证两个不同的枚举不会被认为是 eFeelings

对于更简单的代码，我使用 struct ，因为你可能希望内容是公开的。

如果你正在做任何这些做法，那么你就超出了曲线，可能不需要再进一步细化。

答案：

如果您使用C ++ 11或更高版本，枚举类将隐含范围枚举名称中的枚举值。

使用枚举类将会丢失隐式转换和比较整数类型，但在实践中可能会帮助您标记模糊或错误的代码。

Often, one needs several enumerated types together. Sometimes, one has a name clash. Two solutions to this come to mind: use a namespace, or use 'larger' enum element names. Still, the namespace solution has two possible implementations: a dummy class with nested enum, or a full blown namespace.

I'm looking for pros and cons of all three approaches.

Example:

// oft seen hand-crafted name clash solution
enum eColors { cRed, cColorBlue, cGreen, cYellow, cColorsEnd };
enum eFeelings { cAngry, cFeelingBlue, cHappy, cFeelingsEnd };
void setPenColor( const eColors c ) {
    switch (c) {
        default: assert(false);
        break; case cRed: //...
        break; case cColorBlue: //...
        //...
    }
 }


// (ab)using a class as a namespace
class Colors { enum e { cRed, cBlue, cGreen, cYellow, cEnd }; };
class Feelings { enum e { cAngry, cBlue, cHappy, cEnd }; };
void setPenColor( const Colors::e c ) {
    switch (c) {
        default: assert(false);
        break; case Colors::cRed: //...
        break; case Colors::cBlue: //...
        //...
    }
 }


 // a real namespace?
 namespace Colors { enum e { cRed, cBlue, cGreen, cYellow, cEnd }; };
 namespace Feelings { enum e { cAngry, cBlue, cHappy, cEnd }; };
 void setPenColor( const Colors::e c ) {
    switch (c) {
        default: assert(false);
        break; case Colors::cRed: //...
        break; case Colors::cBlue: //...
        //...
    }
  }

解决方案

The benefit from a namespace (over a class) is that you can use using declarations when you want.

The problem with using a namespace is that namespaces can be expanded elsewhere in the code. In a large project, you would not be guaranteed that two distinct enums don't both think they are called eFeelings

For simpler-looking code, I use a struct, as you presumably want the contents to be public.

If you're doing any of these practices, you are ahead of the curve and probably don't need to scrutinize this further.

Addendum for this rather dated answer:

If you are using C++11 or later, enum class will implicitly scope the enum values within the enum's name.

With enum class you will lose implicit conversions and comparisons to integer types, but in practice that may help you flag ambiguous or buggy code.

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