C++多态实现计算器

#include <iostream>
using namespace std;
class Calculator
{
public:
    int m_Num1;
    int m_Num2;
    virtual int getResult() = 0;
};
class Add : public Calculator
{
public:
    int getResult()
    {
        return this->m_Num1 + this->m_Num2;
    }
};
class Sub : public Calculator
{
public:
    int getResult()
    {
        return this->m_Num1 - this->m_Num2;
    }
};
class Mul : public Calculator
{
public:
    int getResult()
    {
        return this->m_Num1 * this->m_Num2;
    }
};
class Div : public Calculator
{
public:
    int getResult()
    {
        return this->m_Num1 / this->m_Num2;
    }
};
int main(int argc, char **argv)
{
    Calculator *MyCal = new Add;
    MyCal->m_Num1 = 10;
    MyCal->m_Num2 = 12;
    cout << MyCal->getResult() << endl;
    MyCal = new Sub;
    MyCal->m_Num1 = 99;
    MyCal->m_Num2 = 78;
    cout << MyCal->getResult() << endl;
    return 0;
}