图解C++的多态思想

下面给出一个完整的C++代码实例（结合图解，相信大家一定会真正理解多态思想）：

#include<stdio.h>
#include<stdlib.h>
#include<iostream>
#include<iomanip>
using namespace std;


class A
{
public:
int m_data1;
int m_data2;
void func1() {}
void func2() {}
virtual void vfunc1(){}
virtual void vfunc2(){}
};


class B : public A
{
public:
int m_data3;
void func2() {}
virtual void vfunc1(){}
};


class C : public B
{
public:
int m_data1;
int m_data4;
void func2() {}
virtual void vfunc1(){}
};


void main()
{


system("color f1");


cout << "¼Ì³Ð»ùÀàµÄvtable,¸ÄдÐ麯Êý,ʵÏÖͬһֱÁîµ÷Óò»Í¬º¯Êý£º" << endl;


cout << "sizeof(A):" << sizeof(A) << endl;
cout << "sizeof(B):" << sizeof(B) << endl;
cout << "sizeof(C):" << sizeof(C) << endl;


A a;
B b;
C c;
b.m_data1 = 1;
b.m_data2 = 2;
b.m_data3 = 3;


c.m_data1 = 11;
c.m_data2 = 22;
c.m_data3 = 33;
c.m_data4 = 44;
c.A::m_data1 = 111;




cout << "The offset of object b:" << endl;
cout << &b << " : " << "vptr from A" << endl;
cout << &(b.m_data1) << " : " << b.m_data1 << endl;
cout << &(b.m_data2) << " : " << b.m_data2 << endl;
cout << &(b.m_data3) << " : " << b.m_data3 << endl << endl;


cout << "The offset of object c:" << endl;
cout << &c << " : " << "vptr fron B" << endl;
cout << &(c.A::m_data1) << " : " << c.A::m_data1 << endl;
cout << &(c.m_data1) << " : " << c.m_data1 << endl;
cout << &(c.m_data2) << " : " << c.m_data2 << endl;
cout << &(c.m_data3) << " : " << c.m_data3 << endl;
cout << &(c.m_data4) << " : " << c.m_data4 << endl << endl;


system("pause");


}

运行结果：

原理解释：