C++ 编译多态 运行多态

多态是什么？简单来说，就是某段程序调用了一个API接口，但是这个API有许多种实现，根据上下文的不同，调用这段API的程序，会调用该API的不同实现。今天我们只关注继承关系下的多态。

#include <iostream>
#include <stdio.h>

using namespace std;

class Father
{
public:
    int m_fid;
    Father()
    {
        m_fid = 1;
    }
    virtual void v_print()
    {
        printf("Father v_print() %d\n", m_fid);
    }

    void print()
    {
        printf("Father print() %d\n", m_fid);
    }
};

class Child : public Father
{
public:
    int m_cid;
    Child()
    {
        m_cid = 2;
    }
    void v_print()
    {
        printf("Child v_print() %d:%d\n", m_fid, m_cid);
    }

    void print()
    {
        printf("Child print() %d:%d\n", m_fid, m_cid);
    }
};

int main(void)
{
    Father *f = new Father();
    Father *fc = new Child();
    Child *c = new Child();
    Child *cf = (Child*)new Father();


    f->print(); 
    f->v_print();

    fc->print();//静态
    fc->v_print();//动态

    c->print();
    c->v_print();
    
    cf->print();//静态
    cf->v_print();//动态
    
    return 0;
}

 运行结果为：

Father print() 1
Father v_print() 1
Father print() 1
Child v_print() 1:2
Child print() 1:2
Child v_print() 1:2
Child print() 1:0
Father v_print() 1