枚举类可以嵌套吗？ [英] Can enum class be nested?

问题描述

这可以做到吗？

enum A
{
    enum B
    {
        SOMETHING1,
        SOMETHING2
    };

    enum C
    {
        SOMETHING3,
        SOMETHING4
    };
};

如果没有其他解决方案？

If not is there an alternative solution?

此问题的目的：希望/需要执行以下操作：

The purpose of this question: Want/need to be able to do something like this:

enum class ElementaryParticleTypes
{

    enum class MATTER
    {
        enum class MESONS
        {
            PI
        };

        enum class BARYONS
        {
            PROTON,
            NEUTRON
        };

        enum class LEPTONS
        {
            ELECTRON
        };
    };

    enum class ANTI_MATTER
    {
        enum class ANTI_MESONS
        {
            ANTI_PI
        };

        enum class ANTI_BARYONS
        {
            ANTI_PROTON
            ANTI_NEUTRON
        };

        enum class ANTI_LEPTONS
        {
            POSITRON
        };
    };

};

希望使用强类型功能。

推荐答案

否，它们不能以这种方式嵌套。实际上，任何编译器都会拒绝它。

No, they cannot be nested that way. In fact, any compiler would reject it.

如果没有其他解决方案？

If not is there an alternative solution?

这主要取决于您要实现的目标（解决什么问题？）。如果您的目标是能够编写 A :: B :: SOMETHING1 之类的东西，则可以通过以下方式在名称空间中定义它们：

That mostly depends on what you are trying to achieve (solution to what problem?). If your goal is to be able to write something like A::B::SOMETHING1, you could just define them within a namespace, this way:

namespace A
{
    enum B
    {
        SOMETHING1,
        SOMETHING2
    };

    enum C
    {
        SOMETHING3,
        SOMETHING4
    };     
}

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