C++ 枚举重新定义和 C++0x

Question

如果我想在 C++ 中排除枚举和类型重定义的问题，我可以使用代码:

struct VertexType
{
    enum
    {
        Vector2 = 1,
        Vertor3 = 2,
        Vector4 = 3,
    };
};

struct Vector2 { ... };
struct Vector3 { ... };
struct Vector3 { ... };

有没有办法删除枚举上面的包装器。我查看了 C++0x，但没有找到有关解决此问题的其他信息。

Answer 1

因为你在谈论 C++0x，只需使用新的 enum class 语法:

enum class VertexType {
   Vector1 = 1,
   Vector2 = 2,
   Vector4 = 3
};

枚举值只能通过 VertexType 类型访问，如 VertexType::Vector1。

标准中的一些引述:

§7.2/2 [...] The enum-keys enum class and enum struct are semantically equivalent; an enumeration type declared with one of these is a scoped enumeration, and its enumerators are scoped enumerators. [...]

§7.2/10 [...] Each scoped enumerator is declared in the scope of the enumeration.[...]

// example in §7.2/10
enum class altitude { high=’h’, low=’l’ };
void h() {
  altitude a;        // OK
  a = high;          // error: high not in scope
  a = altitude::low; // OK
}