类内函数的override问题-方法

Question:

have a base class with a virtual function:

class Base
{
public:
  virtual void Function();
};
void Base::Function()
{
  cout << "default version" << endl;
}

and a derived template class:

template <class T> class Derived : public Base

{
public:
  virtual void Function();
};
If want to have a way to make Function() be taken from the base class for all types, except some chosen ones?

Solution1: (using type-id  operator)

#include <iostream>
#include <typeinfo>
using namespace std;

class Base
{
public:
    virtual void Function();
};

void Base::Function(){
    cout<<"default version"<<endl;
}

template<typename T>   //using template keyword for type branches
class Derived : Base   //from Base class
{
public:
    virtual void Function();
};


template<typename T>  //using template keyword for type branches
void Derived<T>::Function()
{
    if(typeid(T) == typeid(int)) // check if T is an int
    {
        cout << "overriden version 1\n";
    }
    else if(typeid(T) == typeid(long)) // check if T is a long int
    {
        cout << "overriden version 2\n";
    }
    else // if T is neither an int nor a long
    {
        Base::Function(); // call default version
    }
}

int main()
{
    Derived<int> di;
    Derived<long> dl;
    Derived<float> df;
    
    di.Function();
    dl.Function();
    df.Function();
    return 0;
}

 

同时用template specilization也可以解决这个问题