C++类型向上转换的一种形式

#ifndef _TEST_H#define _TEST_H#include <iostream>#include <string>using namespace std;struct test1{int a;};struct test2{test1 t;int b;int c;};struct test3{test2 t;int d;int e;int f;};void main(){test1 t1;t1.a = 1;test2 t2;t2.t = t1;t2.b = 2;t2.c = 3;test3 t3;t3.t = t2;t3.d = 4;t3.e = 5;t3.f = 6;test1 *pT1 = &t1;test2 *pT2 = &t2;test3 *pT3 = &t3;//这里组织的三个结构体内存分布和三个类一次继承下来的内存分布//是一样的，感觉操作上也非常相似，尤其是向上类型转换和向下类//型转换，和类继承相比限制条件更加少了一下，尤其是向下类型转换。//相当于test2从test1中继承，test3从test1和test2中多继承//相当于向上类型转换pT1 = (test1 *)pT2;cout << pT1->a << endl;//相当于向下类型转换pT2 = (test2 *)pT1;cout << pT2->b << endl;cout << &(pT1->a) << endl;cout << &(pT2->b) << endl;//相当于向上类型转换pT2 = (test2 *)pT3;cout << pT2->t.a << endl;cout << pT2->b << endl;cout << pT2->c << endl;//相当于向下类型转换pT3 = (test3 *)pT2;cout << pT3->d << endl;cout << pT3->e << endl;cout << pT3->f << endl;}#endif //_TEST_H</p>