在类中声明枚举 [英] Declaring an enum within a class

问题描述

在以下代码片段中， Car 类中声明 Color 枚举，并尝试不污染全局命名空间。

  class Car 
 {
 public：
 
 enum Color 
 {
 RED，
 BLUE，
 WHITE 
}; 
 
 void SetColor（Car :: Color color）
 {
 _color = color; 
} 
 
 Car :: Color GetColor（）const 
 {
 return _color; 
} 
 
 private：
 
 Car :: Color _color; 
 
}; 
  

（1）这是一个很好的方法来限制 Color 枚举？或者，我应该在 Car 类之外声明它，但可能在它自己的命名空间或结构中？我今天刚刚看到这篇文章，它主张后者，并讨论一些关于枚举的好点： http://gamesfromwithin.com/stupid-c-tr​​icks-2-better-enums 。

（2）在此示例中， c $ c>够了吗？ （我假设前者更好，只是为了在全局命名空间中声明另一个 Color 枚举，这样，我们至少明确了枚举

解决方案

1. 如果 Color 是特定于 Car 的这就是你限制其范围的方式。如果你要另一个 Color 枚举其他类使用，那么你可以使它是全局的（或至少在 Car ）。




2. 这没什么区别。如果有一个全局变量，那么局部变量仍然被使用，因为它更接近当前范围。注意，如果你在类定义之外定义这些函数，你需要在函数的接口中明确指定 Car :: Color 。

In the following code snippet, the Color enum is declared within the Car class in order to limit the scope of the enum and to try not to "pollute" the global namespace.

class Car
{
public:

   enum Color
   {
      RED,
      BLUE,
      WHITE
   };

   void SetColor( Car::Color color )
   {
      _color = color;
   }

   Car::Color GetColor() const
   {
      return _color;
   }

private:

   Car::Color _color;

};

(1) Is this a good way to limit the scope of the Color enum? Or, should I declare it outside of the Car class, but possibly within its own namespace or struct? I just came across this article today, which advocates the latter and discusses some nice points about enums: http://gamesfromwithin.com/stupid-c-tricks-2-better-enums.

(2) In this example, when working within the class, is it best to code the enum as Car::Color, or would just Color suffice? (I assume the former is better, just in case there is another Color enum declared in the global namespace. That way, at least, we are explicit about the enum to we are referring.)

Thanks in advance for any input on this.

解决方案

1. If Color is something that is specific to just Cars then that is the way you would limit its scope. If you are going to have another Color enum that other classes use then you might as well make it global (or at least outside Car).

2. It makes no difference. If there is a global one then the local one is still used anyway as it is closer to the current scope. Note that if you define those function outside of the class definition then you'll need to explicitly specify Car::Color in the function's interface.

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