获取成员的类型 [英] Getting the type of a member

问题描述

有简单的方法来检索成员类型吗？

在C ++ 03中

Is there an easy way to retrieve the type of a member?
In C++03

struct Person
{
    std::string name;
    int         age;
    double      salary;
};

int main()
{
    std::vector<Person>     people; //  get a vector of people.

    std::vector<GET_TYPE_OF(Person::age)>   ages;

    ages.push_back(people[0].age);
    ages.push_back(people[10].age);
    ages.push_back(people[13].age);

}

我实际上是这样做的（即稍微偷懒）：

I am actually doing this (ie being slightly lazy):

#define BuildType(className, member, type)                                 \
        struct className ## member: TypeBase<className, type>              \
        {                                                                  \
            className ## member()                                          \
                : TypeBase<className, type>(#member, &className::member)   \
            {}                                                             \
        }

BuildType(Person, name,     std::string);
BuildType(Person, age,      int);
BuildType(Person, salary,   double);
typedef boost::mpl::vector<Personname, Personage, Personsalary> FunckyMTPMap;

但不是强制用户指定我想要编译器的成员类型实际生成它。

But rather than have to force the user to specify the type of the member I want to the compiler to generate it pragmatically.

#define BuildType(className, member)                                                  \
struct className ## member: TypeBase<className, TYPE_OF(className ## member)>         \
{                                                                                     \
   className ## member()                                                              \
      : TypeBase<className, TYPE_OF(className ## member)>(#member, &className::member)\
   {}                                                                                 \
}
BuildType(Person, name);
BuildType(Person, age);
BuildType(Person, salary);
typedef boost::mpl::vector<Personname, Personage, Personsalary> FunckyMTPMap;

推荐答案

template <class T, class M> M get_member_type(M T:: *);

#define GET_TYPE_OF(mem) decltype(get_member_type(mem))

<是C ++ 11的方式。它要求您使用& Person :: age 而不是 Person :: age ，虽然您可以轻松调整宏来使&符隐式。

Is the C++11 way. It requires you to use &Person::age instead of Person::age, although you could easily adjust the macro to make the ampersand implicit.

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