符合标准的typedef我的枚举方式 [英] standards compliant way to typedef my enums

问题描述

如何正确地清除该枚举的范围，如何摆脱警告？符合标准的代码将与 foo :: bar :: mUpload 进行比较（请参阅这里），但显式的范围真的很长，并且使darn的东西不可读。

<可能还有另一种不使用typedef的方法？我不想修改枚举 - 我没有写它，它在其他地方使用。

警告C4482：使用非标准扩展：enum'foo :: bar :: baz'用于限定名称

  namespace foo {
 class bar {
 enum baz {mUpload = 0，mDownload}; 
} 
} 
 
 typedef foo :: bar :: baz mode_t; 
 mode_t mode = getMode（）; 
 
 if（mode == mode_t :: mUpload）// C4482 
 {
 return uploadthingy（）; 
} 
 else 
 {
 assert（mode == mode_t :: mDownload）; // C4482 
 return downloadthingy（）; 
} 
  

解决方案

一个类，你可以做的最好的就是把类放入你自己的范围，只需使用 class_name :: value 或定义类的typedef。在C ++ 03中，枚举的值是封闭范围的一部分（在你的情况下是类）。在C ++ 0x / 11中，您将能够使用枚举名称限定值：

  namespace first {namespace second { 
 struct closure {
 enum the_enum {one_value，another}; 
} 
}} 
使用第一::第二::封闭; 
 typedef first :: second :: encing the_enclosing; 
 
 assert（enclosureing :: one_value！= the_enclosing :: another）; 
  

将来，您的使用将是正确的（C ++ 11）：

  typedef first :: second :: enclosureing :: the_enum my_enum; 
 assert（my_enum :: one_value！= my_enum :: another）; 
  

How can I get rid of the warning, without explicitly scoping the enum properly? The standards-compliant code would be to compare against foo::bar::mUpload (see here), but the explicit scopes are really long and make the darn thing unreadable.

maybe there's another way that doesn't use typedef? i don't want to modify the enum--i didn't write it and its in use elsewhere.

warning C4482: nonstandard extension used: enum 'foo::bar::baz' used in qualified name

namespace foo { 
class bar { 
enum baz {mUpload = 0, mDownload};
}
}

typedef foo::bar::baz mode_t;
mode_t mode = getMode(); 

if (mode == mode_t::mUpload) //C4482
{
 return uploadthingy();
}
else 
{
 assert(mode == mode_t::mDownload); //C4482
 return downloadthingy();
}

解决方案

If the enum is defined within a class, the best that you can do is bring the class into your own scope and just use class_name::value or define a typedef of the class. In C++03 the values of an enum are part of the enclosing scope (which in your case is the class). In C++0x/11 you will be able to qualify the values with the enum name:

namespace first { namespace second {
   struct enclosing {
      enum the_enum { one_value, another };
   }
}}
using first::second::enclosing;
typedef first::second::enclosing the_enclosing;

assert( enclosing::one_value != the_enclosing::another );

In the future, your usage will be correct (C++11):

typedef first::second::enclosing::the_enum my_enum;
assert( my_enum::one_value != my_enum::another );

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