学步园

#include <iostream>

/* run this program using the console pauser or add your own getch, system("pause") or input loop */

using namespace std;

class Parent
{
protected:
	int i;
public:
	virtual void f()
	{
		cout<<"Parent::f()"<<endl;
	}
}; 

class Child: public Parent
{
protected:
	int j;
public:
	Child(int i, int j)
	{
		this->i = i;
		this->j = j;
	}
	virtual void f()
	{
		cout<<"i = "<<i<<"  "<<"j = "<<j<<endl; 
	}
};

int main(int argc, char** argv) {
	
	Parent* p = NULL;
	Child* c = NULL;
	Child ca[3] = {
		Child(1,2),
		Child(2,3),
		Child(3,4)
	};
	
	p = ca;
	c = ca;
	
	/*
	不要将多态应用于数组
? 指针运算是通过指针的类型进行的
? 多态通过虚函数表实现的
	*/
	cout<<hex<<&ca[0]<<endl;
	cout<<sizeof(Parent)<<endl;
	cout<<hex<<&ca[1]<<endl;
	
	cout<<hex<<p+1<<endl; 
	
	/*
	Parent占8个字节，Child占12个字节，指针运算是按照指针类型来运算的，p+1，即P+8个字节。而ca[0]与ca[1]相距12个字节 
0x22feb4
8
0x22fec0
0x22febc
i = 1  j = 2
i = 1  j = 2
i = 2  j = 3
	*/
	p->f();
	c->f();
	
	p++;
	c++;
	//p->f();
	c->f();
	return 0;
}

P++ ; 等价于 p = p+1；

p+1； (unsigned int )p + 1*sizeof(*p);

Parent占8个字节，Child占12个字节，指针运算是按照指针类型来运算的，p+1，即P+8个字节。而ca[0]与ca[1]相距12个字节

0x22feb4

80x22fec

00x22febc

i = 1 j = 2

i = 1 j = 2

i = 2 j = 3

所以不要在数组上使用多态！！！！