C++多态

C++

发布日期: 2023-12-10

更新日期: 2022-11-12

文章字数: 387

阅读时长: 2 分

阅读次数:

#include <iostream>
using namespace std;
class Wood{
protected:
    int height;
    int cost;
public:
    Wood(int height,int cost)
    {
        this->height=height;
        this->cost=cost;
    }
    virtual void show()
    {
        cout<<height<<endl;
    }
};
class Table:public Wood{
public:
    Table(int height,int cost): Wood(height,cost){}
    void show()
    {
        cout<<"Table:"<<height<<endl;
    }
};
int main()
{
    Table t1(55,61);
	Wood *ptr=&t1;
    ptr->show(); // Table:55
    return 0;
}

2021-5-22-15-53

当类中出现了虚函数，该类中就会生成一个虚函数指针，该虚函数指针指向虚函数表，虚函数表实质上来说是一个数组
当基类中有虚函数时，派生类中也会生成一个虚函数指针，指向虚函数表，这个表继承了基类虚函数表的元素
如果重写虚函数就会修改虚函数表的内容，让其指向自己的函数

#include <iostream>
using namespace std;
class Wood{
public:
    Wood(int height,int cost)
    {
        this->height=height;
        this->cost=cost;
    }
    virtual void show()
    {
//        cout<<height<<endl;
        cout<<"hell"<<endl;

    }
protected:
    int height;
    int cost;
};
class Table:public Wood{
public:
    Table(int height,int cost): Wood(height,cost){}
    void show()
    {
        cout<<"Table:"<<height<<endl;
    }
};
typedef void (*Myfunc)();
int main()
{
    Wood w1(12,36);
    Table t1(55,61);
    long long *wptr=(long long *)(((long long *)(*((long long *)&w1)))[0]);
    long long *tptr=(long long *)(((long long *)(*((long long *)&t1)))[0]);
    Myfunc ptr=(Myfunc)wptr;
    ptr(); // hell
    cout<<wptr<<endl; //0x402d80
    cout<<tptr<<endl; //0x402e40
    return 0;
}