特定基类的 C++ 类模板

Question

假设我有类(class):

class Base{};

class A: public Base{
    int i;
};

class B:public Base{
    bool b;
};

现在我想定义一个模板类:

template < typename T1, typename T2 >
class BasePair{
    T1 first;
    T2 second;
};

但我想将其定义为只有 Base 类的后代可以用作模板参数。

我该怎么做？

Answer 1

C++11 引入 <type_traits>

template <typename T1, typename T2>
class BasePair{
static_assert(std::is_base_of<Base, T1>::value, "T1 must derive from Base");
static_assert(std::is_base_of<Base, T2>::value, "T2 must derive from Base");

    T1 first;
    T2 second;
};