燕山大学-面向对象程序设计实验-实验6 派生与继承：多重派生-实验报告

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实验六 派生与继承—多重派生

🚩6.1 实验目的

1．理解多重派生的定义；

2．理解多重派生中构造函数与析构函数的调用顺序；

3．理解多重派生中虚拟基类的作用；

🚩6.2 实验内容

🚩6.2.1程序阅读

1．理解下面的程序，并在VC++6.0下运行查看结果，回答程序后面的问题。

class CBase1{public:CBase1(int a):a(a){cout<<"base1 structure..."<<endl;}~CBase1(){cout<<"base1 destructure..."<<endl;}void print(){cout<<"a="<<a<<endl;}protected:int a;};class CBase2{public:CBase2(int b):b(b){cout<<"base2 structure..."<<endl;}~CBase2(){cout<<"base2 destructure..."<<endl;}void print(){cout<<"b="<<b<<endl;}protected:int b;};class CDerive : public CBase1, public CBase2{public:CDerive(){cout<<"derive structure..."<<endl;}~CDerive(){cout<<"derive destructure..."<<endl;}void print(){CBase1::print();CBase2::print();b1.print();b2.print();cout<<"c="<<c<<endl;}private:CBase1 b1;CBase2 b2;int c;};void main(){CDerive d;d.print();}

问题一：改正以上程序中存在的错误，并分析该程序的输出结果。

答：（1）没有引用头文件，且未声明命名空间。
（2）CBase1和CBase2类缺少默认的构造函数。
分析：main函数创建CDerive类对象d时，CDerive类继承了CBase1和CBase2类，因此输出了前两行。在CDerive类中又有两个成员对象b1和b2，再次调用CBase1和CBase2的构造函数，故有3、4行。随后，CDerive构造函数中有输出第5行内容。6-10行为CDerive::print()函数中内容，由于在调用时均为赋值，因此变量内容不确定。后5行为析构，与构造过程相反。

2．理解下面的程序，并在VC++6.0下运行查看结果，回答程序后面的问题。

#include "iostream"class CBase{public:CBase(int a):a(a){}int a;};class CDerive1 : public CBase{public:CDerive1(int a):CBase(a){}};class CDerive2 : public CBase{public:CDerive2(int a):CBase(a){}};class CDerive : public CDerive1,public CDerive2{public:CDerive(int a,int b):CDerive1(a),CDerive2(b){}};void main(){CDerive d(1,2);cout<<d.a<<endl;}

问题一：在不改变原有程序意图的前提下，分别用三种方法改正以上程序，并使程序正确输出。

答：（1）方法一：使用虚继承

#include <iostream>using namespace std;class CBase   {public:CBase(int a):a(a){}int a;};class CDerive1 : virtual public CBase{public:CDerive1(int a):CBase(a){}};class CDerive2 :virtual public CBase{public:CDerive2(int a):CBase(a){}};class CDerive : public CDerive1,public CDerive2{public:CDerive(int a,int b):CDerive1(a),CDerive2(b),CBase(b){}};int main(){CDerive d(1,2);cout<<d.a<<endl;return 0;}

2）添加输出函数print()

#include <iostream>using namespace std;class CBase {public:CBase(int a):a(a){}int a;int print(){return a;}};class CDerive1 : public CBase{public:CDerive1(int a):CBase(a){}};class CDerive2 :public CBase{public:CDerive2(int a):CBase(a){}};class CDerive : public CDerive1,public CDerive2{public:CDerive(int a,int b):CDerive1(a),CDerive2(b){}int print(){return CDerive1::print();}};int main(){CDerive d(1,2);cout<<d.print()<<endl;return 0;}

（3）获取变量时限定作用域

#include <iostream>using namespace std;class CBase {public:CBase(int a):a(a){}int a;};class CDerive1 : public CBase{public:CDerive1(int a):CBase(a){}};class CDerive2 :public CBase{public:CDerive2(int a):CBase(a){}};class CDerive : public CDerive1,public CDerive2{public:CDerive(int a,int b):CDerive1(a),CDerive2(b){}int getA(){return CDerive1::a;}};int main(){CDerive d(1,2);cout<<d.getA()<<endl;return 0;}

🚩6.2.2 程序设计

1．建立普通的基类building，用来存储一座楼房的层数、房间数以及它的总平方数。建立派生类house，继承building，并存储卧室与浴室的数量，另外，建立派生类office，继承building，并存储灭火器与电话的数目。设计一主函数来测试以上类的用法。

答：

#include<iostream>using namespace std;class building{protected:int floor;int room_num;int area;public:building(int a,int b,int c):floor(a),room_num(b),area(c){}void buildingInfo(){cout<<"* 楼层:"<<floor<<endl;cout<<"* 房间数："<<room_num<<endl;cout<<"* 面积："<<area<<endl;}};class house:public building{private:int sleep_num;int wash_num;public:house(int a,int b,int c,int d,int e):building(a,b,c),sleep_num(d),wash_num(e){}void houseInfo(){cout<<"住宅："<<endl;buildingInfo();cout<<"* 卧室数量："<<sleep_num<<endl;cout<<"* 浴室数量："<<wash_num<<endl;}};class office:public building{private:int fire_num;int phone_num;public:office(int a,int b,int c,int d,int e):building(a,b,c),fire_num(d),phone_num(e){}void officeInfo(){cout<<"办公室："<<endl;buildingInfo();cout<<"* 灭火器数量："<<fire_num<<endl;cout<<"* 电话数量："<<phone_num<<endl;}};int main(){house h(10,5,300,2,1);office o(5,10,500,20,10);h.houseInfo();o.officeInfo();return 0;}

🚩6.3思考题

1．按照下图的类层次结构编写程序，定义属于score的对象c1以及类teacher的对象t1，分别输入每个数据成员的值后再显示出这些数据。

答：

#include<iostream>#include<cstring>#include<string>using namespace std;class person{protected:string name;int id;public:person(string a,int b):name(a),id(b){}void personInfo(){cout<<"* 姓名："<<name<<endl;cout<<"* ID："<<id<<endl;}};class teacher:public person{private:string degree;string dep;public:teacher(string a,int b,string c,string d):person(a,b),degree(c),dep(d){}void teacherInfo(){cout<<"教师信息："<<endl;personInfo();cout<<"* 学历："<<degree<<endl;cout<<"* 部门："<<dep<<endl;}};class student:public person{private:int old;int sno;public:student(string a,int b,int c,int d):person(a,b),old(c),sno(d){}void studentInfo(){cout<<"学生信息："<<endl;personInfo();cout<<"* 年龄："<<old<<endl;cout<<"* 学号："<<sno<<endl;}};class stud{protected:string addr;string tel;public:stud(string a,string b):addr(a),tel(b){}void studInfo(){cout<<"* 住址："<<addr<<endl;cout<<"* 电话："<<tel<<endl;}};class score:public student,public stud{private:double math;double eng;public:score(string a,int b,int c,int d,string e,string f,double s1,double s2):student(a,b,c,d),stud(e,f),math(s1),eng(s2){}void scoreInfo(){studentInfo();studInfo();cout<<"* 数学成绩："<<math<<endl;cout<<"* 英语成绩："<<eng<<endl;}};int main(){score a("张三",10086,20,2020123456,"四川省成都市犀安路999号","15866668888",88.8,98.7);a.scoreInfo();teacher b("李四",10010,"博士","计算机学院");b.teacherInfo();return 0;}

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