我可以参考模板的基础 class 吗？

Question

Is there a way to refer to the base class of the currently provided template? For example,

template <class UserType>
class User
{
    public:
        User()
        {
            user_manager_ = std::make_unique<UserType>();
        }

   private:
        std::unique_ptr<UserType::Base> user_manager_; // <-- I want this ptr to be the type of base of UserType i.e. IUserManager
}

Answer 1

Nope, because of multiple inheritances in c++. The only way to do something similar is:

struct A {};

struct UserType : public A {
  using Base = A;
};

template<class UserType>
class User {
 public:
  User() {
    user_manager_ = std::make_unique<UserType>();
  }

 private:
  std::unique_ptr<typename UserType::Base> user_manager_; // <-- I want this ptr to be the type of base of UserType i.e. IUserManager
};