如何根据运行时输入实例化 c++ 模板？

Question

我定义了一个模板函数，想根据不同的输入调用不同的特化：

// function
template <typename T>
void f() {...}

// specialization 1
template <>
void f<C1>() { ... }

// specialization 2
template <>
void f<C2>() { ... }


// class 
class Cbase {};

class C1 : Cbase {};

class C2 : Cbase {};

int main()
{
    std::string s = input();
    Cbase* c;

    if (s == "c1")
    {
      // here I want to use `specialization 1` but not 
      // call immediately here but later, so I create an instance of C1
      c = new C1;
    }
    else
    {
      // here I want to use `specialization 2` but not
      // call immediately here but later, so I create an instance of C2
     c = new C2;
    }

    // Is there a way to call specializations according to the type of `c`? 
    // Can I get the type in the runtime to call the particular 
    // template specializations I want?
}

有没有办法根据 c 调用专业化？我可以在运行时获取类型来调用我想要的特定模板特化吗？

Answer 1

没有。根据定义，模板是编译时构造。如果您需要运行时多态性，那么您基本上应该寻找虚函数。

Answer 2

将您的程序重组为：

template <typename T>
void main_function()
{
    T c;

    // f<T>();
    // ...
}

int main()
{
    std::string s = input();

    if (s == "c1")
    {
        main_function<C1>();
    }
    else
    {
        main_function<C2>();
    }
}