81.类成员函数指针高级

#include <iostream>
using namespace std;

//myclass类
class myclass
{
public:
    int add(int a, int b)
    {
        return a + b;
    }
    int sub(int a, int b)
    {
        return a - b;
    }
    int mul(int a, int b)
    {
        return a * b;
    }
    int divv(int a, int b)
    {
        return a / b;
    }
};

//类成员函数当做引用参数
void change(int(myclass::*&p)(int, int))
{
    p = &myclass::sub;
}

//changeit的参数是类成员函数指针的引用,返回值是类成员函数指针的引用
//类成员函数指针作为参数退化为二级类成员函数指针
int(myclass::*&  changit(  int(myclass::* &p)(int, int)  )  )(int, int)
{
    p = &myclass::sub;
    return p;
}

void main()
{
    myclass *pclass(nullptr);//空指针
    //int(myclass::*p)(int, int) = &myclass::add;//类成员函数指针
    //cout << pclass->add(1, 2) << endl;
    //cout << (pclass->*p)(2, 3) << endl;
    int(myclass::*p[4])(int, int) { &myclass::add, &myclass::sub, &myclass::mul, &myclass::divv };
    //下标方式循环
    for (int i = 0; i < 4; i++)
    {
        //调用类成员函数数组
        cout << (pclass->*p[i])(100, 10) << endl;
    }

    //指针方式循环(二级类成员函数指针遍历类成员函数指针)
    for (int(myclass::**pp)(int, int) = p; pp < p + 4; pp++)
    {
        cout << (pclass->**pp)(100, 10) << endl;
    }

    //在堆上创建类成员函数指针
    int (myclass::**p2)(int,int) = new (int(myclass::*[4])(int,int)){ &myclass::add, &myclass::sub, &myclass::mul, &myclass::divv };
    for (int i = 0; i < 4; i++)
    {
        //调用类成员函数数组
        cout << (pclass->*p2[i])(100, 10) << endl;
    }

    int(myclass::*p3)(int, int) = &myclass::add;
    change(p3);
    (pclass->*p3)(12, 2);
    cin.get();
}