来自指针的类类型用作模板参数 [英] Class type from pointer used as template argument

问题描述

如果将用户定义类型的指针作为模板参数传递给模板类，是否可以获得参数的类类型?

If a pointer to an user defined type is passed as template argument to a template class, is it possible to get the class type of the argument?

template <class T> struct UserType {
    typedef T value_type;
    ...
};

int main () {
    typedef std::vector<UserType<double>*> vecType
    vecType vec;

    vecType::value_type::value_type m; //how to get the double here?

    return 0;
}

推荐答案

使用特征:

template <typename> struct ptr_traits {};
template <typename T> struct ptr_traits<T*>
{ typedef T value_type; };

ptr_traits<vecType::value_type>::value_type m;

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