内蒙古科技大学面向对象的程序设计实验 静态成员和友元

1、内蒙古科技大学面向对象的程序设计实验报告  课程名称：面向对象的程序设计姓名：陈伟光实验名称：静态成员和友元学号：1567159118任课教师：刘月峰专业：软件工程指导教师：刘月峰班级：15-软件一班  一、实验目的  1理解静态成员（静态数据成员、静态成员函数）的作用与使用；2理解友元（友元函数、友元类）的作用于使用。二、实验环境编译器：Visual C+ 6.0.操作系统：Windows 7 旗舰版 三、实验内容 二、实验内容2.1练习（一）：1理解下面的程序，并在VC+6.0下运行查看结果，回答程序

2、后面的问题。#include <iostream.h>#include <string.h>class CStudentpublic:CStudent(char *n, int a);CStudent();static void SetAge(int age);private:char *name;int age;static int nTotalObj;int CStudent:nTotalObj = 0;CStudent:CStudent(char *n, int a):age(a)int nLen = strlen(n);name = new charnLen+1

3、;strcpy(name,n);namenLen = 0;nTotalObj+;CStudent:CStudent()delete name;nTotalObj-;void CStudent:SetAge(int age)this->age = age;void main()CStudent stu1("张三",25);CStudent str2("李四",26);cout<<"CStudent:nTotalObj="<<CStudent:nTotalObj<<endl;问题一：以上程序编译能

4、通过吗，为什么？问题二：成员变量nTotalObj在程序中起什么作用，它是如何实现的？问题三：如果规定该程序的主函数和类CStudent中的成员变量的属性不允许改变，应该如何改正该程序？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.h>#include <string.h>class CStudentpublic:CStudent(char *n, int a);CStudent();private:char *name;int age;CStudent:CStudent(char *n, int a):ag

5、e(a)int nLen = strlen(n);name = new charnLen+1;strcpy(name,n);namenLen = 0;CStudent:CStudent()delete name;class CTeacherpublic:CTeacher(char *tn, int ta);CTeacher();void SetStuAge(int a); private:char *name;int age;CStudent stu;CTeacher:CTeacher(char *tn, int ta):age(ta)int nLen = strlen(tn);na

6、me = new charnLen+1;strcpy(name,tn);namenLen = 0;CTeacher:CTeacher()delete name;void CTeacher:SetStuAge(int a)stu.age = a;void main()CStudent stu("张三",25);CTeacher tea("李四",26);问题一：以上程序有两大错误，试指出来，并改正之？2.2练习（二）：1某商店经销一种货物。货物成箱购进，成箱卖出，购进和卖出时以重量为单位，各箱的重量不一样，因此，商店需要记录下货物库存的总重量。试用C+模拟

7、商店货物购进和卖出的情况。（提示：将总重量定义为静态成员）四、实验过程练习1 题目提供源代码如下编译结果如下分析之后得出结论首先静态成员函数SetAge中不可以使用指针，也不可以直接使用非静态数据成员age 此处应该使用对象名或者类名间接引用age 其次nTotalObj为私有属性，不可以直接访问，且题目要求不可以修改其属性，则添加一个成员函数，使其返回值等于nTotalObj,则代替了原先nTotalObj的功能 修改之后的代码如下然后再次编译运行结果如下运行结果正确，且不影响nTotalObj的计数器功能，代码修改正确 练习2题目提供源代码如下编译之后结果如下

8、分析错误原因有两点错误1 CTeacher类中的成员函数SetStuAge不能直接访问CStudent类内嵌成员stu的数据成员age错误2 CTeacher类构造函数的初始化含有错误,内嵌对象stu的数据成员也应该包含在内 修改之后代码如下运行结果如下成功运行，修改正确 练习3根据题意，所编写代码如下尝试测试运行结果该代码包含题目要求的所有功能，运行完毕 五、实验总结实验源代码:练习（一）  /修改之后代码#include <iostream.h>#include <string.h>class CStudentpub

9、lic:      CStudent(char *n, int a);      CStudent();      static void SetAge(CStudent stuN);      static int CSnTota10bj();         

10、60;          private:      char *name;      int age;      static int nTotalObj;int CStudent:nTotalObj = 0;CStudent:CStudent(char *n, int a):age(a)  &#

11、160;   int nLen = strlen(n);      name = new charnLen+1;      strcpy(name,n);      namenLen = 0;      nTotalObj+;        

12、0;                           CStudent:CStudent()      delete name;      nTotalObj-; int CStudent:CSn

13、Tota10bj()      int n;      n=nTotalObj;      return n; void CStudent:SetAge(CStudent stuN)      int a;      stuN.age = a;void main()  

14、    CStudent stu1("张三",25);      CStudent str2("李四",26);      cout<<"CStudent:nTotalObj="<<CStudent:CSnTota10bj()<<endl;练习（二） #include <iostream.h>#include <s

15、tring.h>class CStudentpublic:      CStudent(char *n, int a);      CStudent();private:      char *name;public:      int age;CStudent:CStudent(char *n, int a):age(a)  &#

16、160;   int nLen = strlen(n);      name = new charnLen+1;                             strcpy(name,n); 

17、0;    namenLen = 0;CStudent:CStudent()      delete name;class CTeacherpublic:      CTeacher(char *tn,int ta,char *sn,int sa);      CTeacher();      void SetStuA

18、ge(int a);private:      char *name;      int age;      CStudent stu;                       

19、0;                  CTeacher:CTeacher(char *tn,int ta,char *sn="noname",int sa=0):age(ta),stu(sn,sa)      int nLen = strlen(tn);      name =

20、 new charnLen+1;      strcpy(name,tn);      namenLen = 0;CTeacher:CTeacher()      delete name;void CTeacher:SetStuAge(int a)      stu.age = a;void main()    

21、60; CStudent stu("张三",25);      CTeacher tea("李四",26);  /*错误1 CTeacher类中的成员函数SetStuAge不能直接访问CStudent类内嵌成员stu的数据成员age错误2 CTeacher类构造函数的初始化含有错误,内嵌对象stu的数据成员也应该包含在内*/ 练习（三）  #include <iostream.h>class Goodsprivate:

22、60;   int weight;    static int totalWeight;public:    Goods(int wei);    static void PrintTotalWeight();    void sell();       void buy();int Goods:totalWeight = 0;Goods

23、:Goods(int twei)    totalWeight = twei;       cout<<"初始总重量为:"<<totalWeight<<endl; void Goods:PrintTotalWeight()    cout<<"总重量为:"<<Goods:totalWeight<<endl;void Goods

24、:buy()       cout<<"购入"<<endl;       cout<<"请输入购入货物的重量:"       cin>>weight;    Goods:totalWeight += weight;    

25、                     weight  = 0;void Goods:sell()       cout<<"售出"<<endl;       cout<<

26、"请输入售出货物的重量:"       cin>>weight;    Goods:totalWeight -= weight;                           

27、60;                   weight  = 0;void main()       int twei=0;       int swit=1;       co

28、ut<<"请设置初设总重量"<<endl;       cin>>twei;    Goods goods1(twei);       while(swit)                 &

29、#160;                cout<<"请选择操作类型:0.退出  1.购入  2.售出"<<endl;              cin>>swit;   

30、            switch(swit)                                  case 0:cout&

31、lt;<endl;                     break;              case 1:goods1.buy();                            goods1.PrintTotalWeight();