理解object slicing

最新推荐文章于 2025-05-20 11:55:12 发布

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最新推荐文章于 2025-05-20 11:55:12 发布

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分类专栏： C++ 文章标签： object 编译器

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本文通过一个家族成员的类结构示例，展示了 C++ 中如何使用继承和多态来实现运行时的多态行为。示例中包含了基类 Grandfather 和派生类 Father、Uncle 以及 Son 的定义，演示了静态绑定和动态绑定的区别。

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摘自：http://blog.youkuaiyun.com/RayChase/archive/2008/03/27/2223381.aspx

#include <iostream>
using namespace std;
class Grandfather...{
public:
    virtual void display()=0;
    void run()...{
        cout<<"Grandfather Run!!! ";
    }
};
class Father:public Grandfather...{
public:
    int fatherValue;
    void display()...{
        cout<<"Father Display!! ";
    }
    void run()...{
        cout<<"Father Run!!! ";
    }
};
class Uncle:public Grandfather...{
public:
    int uncleValue;
    void display()...{
        cout<<"Uncle Display!! ";
    }
    void run()...{
        cout<<"Uncle Run!!! ";
    }
};
class Son:public Father...{
public:
    int sonValue;
    void display()...{
        cout<<"Son Display!! ";
    }
};
void main()...{
    Grandfather* grandfather_pt=NULL;
    Father* father_pt=NULL;
    Son* son_pt=NULL;

    Father father;
    Uncle uncle;
    Son son;

    cout<<"静态绑定不用virtual关键字： ";
    grandfather_pt=&uncle;
    grandfather_pt->run();
    grandfather_pt=&father;
    grandfather_pt->run();

    cout<<" 动态绑定纯虚函数： ";
    grandfather_pt=&uncle;
    grandfather_pt->display();
    grandfather_pt=&father;
    grandfather_pt->display();

    cout<<" 指针强制转换 ";
    ( (Father*)(&son) )->display();
//    ( (Father*)(&son) )->run();

    cout<<" 对象强制转换 ";
    ((Father)son).display();        //只允许upcasting，不允许downcasting
    cout<<" 编译器为了防止对象切割的发生，自动调用拷贝构造函数，因此，比较地址： ";
    cout<<( father_pt=&((Father)son) )<<endl;    //注意优先级
    cout<<&son<<endl;
    cout<<"发现二者不同！ ";
}