如何使用枚举作为C ++中的标志？ [英] How to use enums as flags in C++?

问题描述

通过 [Flags] 属性，处理枚举作为标志在C＃中工作得很好，但是最好的方法是什么在C ++中这样做？

例如，我想写：

  enum AnimalFlags 
 {
 HasClaws = 1，
 CanFly = 2，
 EatsFish = 4，
 Endangered = 8 
} 
 
 seahawk.flags = CanFly | EatsFish |濒危;但是，我遇到了关于 int 的编译器错误。  / 枚举转换。有没有更好的方式来表达这不只是钝的铸造？优选地，我不想依赖于第三方库（例如boost或Qt）的构造。
 
 
 
编辑：如答案所示，我可以避免编译器错误通过将 seahawk.flags 声明为 int 。但是，我想有一些机制来强制类型安全，所以有人不能写 seahawk.flags = HasMaximizeButton 。
 
 code> enum AnimalFlags 
 {
 HasClaws = 1，
 CanFly = 2，
 EatsFish = 4，
 Endangered = 8 
} 
 
 inline AnimalFlags运算符|（AnimalFlags a，AnimalFlags b）
 {return static_cast< AnimalFlags>（static_cast< int>（a）| static_cast< int>（b））;} 
  
等。其余的位运算符。如果枚举范围超出了int范围，请根据需要进行修改。
 
Treating enums as flags works nicely in C# via the [Flags] attribute, but what's the best way to do this in C++?

For example, I'd like to write:
enum AnimalFlags
{
    HasClaws = 1,
    CanFly =2,
    EatsFish = 4,
    Endangered = 8
};

seahawk.flags = CanFly | EatsFish | Endangered;
However, I get compiler errors regarding int/enum conversions.  Is there a nicer way to express this than just blunt casting?  Preferably, I don't want to rely on constructs from 3rd party libraries such as boost or Qt.

EDIT: As indicated in the answers, I can avoid the compiler error by declaring seahawk.flags as int.  However, I'd like to have some mechanism to enforce type safety, so someone can't write seahawk.flags = HasMaximizeButton.
解决方案
The "correct" way is to define bit operators for the enum, as:
enum AnimalFlags
{
    HasClaws = 1,
    CanFly =2,
    EatsFish = 4,
    Endangered = 8
};

inline AnimalFlags operator|(AnimalFlags a, AnimalFlags b)
{return static_cast<AnimalFlags>(static_cast<int>(a) | static_cast<int>(b));}
Etc. rest of the bit operators. Modify as needed if the enum range exceeds int range.

                        
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