虚函数注意点：参数

1。当基类指针调用子类函数时候，缺省实参是由基类决定的。

#include <iostream>
using namespace std;

class A
{
public:
virtual void Fun(int number = 10)
    {
        std::cout << "A::Fun with number " << number<<endl;
    }
};

class B: public A
{
public:
virtual void Fun(int number = 20)
    {
        std::cout << "B::Fun with number " << number<<endl;
    }
};

int main()
{
    B b;
    A &a = b;
    a.Fun();
return 0;//输出结果10
}