将枚举（在结构内部声明）值分配给该结构内部具有相同枚举类型的变量

Question

I have a structure of below type

struct enumStruct
{
    enum Number
    {
        zero = 0,
        one = 1
    };

    Number t;

    union
    {
        /* t = 0 */
        some_struct_zero zero;
        /* t = 1 */
        some_struct_one one;
    } un;
} v_enumStruct;

Can I assign a value to v_enumStruct.t as below?

v_enumStruct.t = v_enumStruct.zero;//Option 1

Also, the below does not seem to work

v_enumStruct.t = zero; //Option 2 - zero is mistaken as an unavailable variable name

Answer 1

1) zero is not a member of struct . 2) The enum inside struct doesn't declare any member. It can be declared anywhere. enum members are named constants, they are not variables and 3) Number needs the enum qualifier:

    struct enumStruct
    {
        enum Number
        {
            zero = 0,
            one = 1
        };
        enum Number t;

        union
        {
         /* t = 0 */
         some_struct_zero zero;
         /* t = 1 */
        some_struct_one one;
        } un;

} v_enumStruct;

You might as well move the enum Number { ..}; outside the struct as it's not doing anything inside the struct. Now you should be able to assign:

v_enumStruct.t = zero;