第三次上机报告.doc

实验三
学号: 姓名: 班级:软件工程141
继承与派生(4学时)
一、实验目得
1.学习定义与使用类得继承关系,定义派生类。
2.熟悉不同继承方式下对基类成员得访问控制。
3.学习利用虚基类解决二义性问题。
二、实验任务
1.定义一个基类Animal,有私有整型成员变量age,构造其派生类dog,在其成员函
数SetAge(int n)中直接给age赋值,瞧瞧会有什么问题,把age改为公有成员变量,还会
有问题吗?编程试试瞧。
2.定义一个基类BaseClass,有整型成员变量Number,构造其派生类DerivedClass,
观察构造函数与析构函数得执行情况。
3、 分析并调试以下程序运行结果,并与实际运行结果相对照。
#include <iostream>
using namespace std;
class Base
{
int x;
public:
Base(int i)
{
x=i;
cout<<"Constuctor of Base"<<endl;
}
~Base{
cout<<"Destuctor of Base"<<endl;
}
void show
{
cout<<"x="<<x<<endl;
}
};
class Derived:public Base
{
Base d;
public:
Derived(int i):Base(i),d(i)
{
cout<<"Constuctor of Derived"<<endl;
}
~Derived
{
cout<<"Destuctor of Derived"<<endl;
}
};
int main( )
{
Derived obj(5);
obj、show;
return 0;
}
4.定义一个车(vehicle)基类,具有MaxSpeed、Weight等成员变量,Run、Stop等成
员函数,由此派生出自行车(bicycle)类、汽车(motorcar)类。自行车(bicycle)类有高度
(Height)等属性,汽车(mot orcar)类有座位数(SeatNum)等属性。从bicycle与motorcar
派生出摩托车(motorcycle)类。
在继承过程中,注意把vehicle设置为虚基类。如果不把vehicle设置为虚基类,会有什么问题?编程试试瞧。
5.设计people(人员)类,考虑到通用性,抽象出所有类型人员都具有得属性:number(编号)、sex(性别)、birthday(出生日期)、id(身份证号)等等。派生出student(学生)类,添加属性:班号char classNO[7];从people类派生出teacher(教师)类,添加属性:职务char principalship[11]、部门char departmentE21]。从student类中派生出graduate(研究生)类,添加属性:专业char subject[21]、导师teacher adviser;从graduate类与teacher类派生出TA(助教生)类,注意虚基类得使用。重载相应得成员函数,测试这些类。
三、实验步骤
1、若将age设置为私有成员,在其派生类中直接给其赋值,会出现错误提示:
将age设置为公有成员时,能正常运行
代码:
#include<iostream>
using namespace std;
class Animal
{
public:
int age;
};
class dog:public Animal
{
public:
int setAge(int n)
{age=n; return age;}
};
int main
{
dog d;
cout<<d、setAge(3)<<endl;
return 0;
}
运行结果为:

2、执行情况为:(1)基类BaseClass得构造函数;
(2)派生类DerivedClass得构造函数;
(3)派生类DerivedClass得析取函数;
(4)基类BaseClass得析取函数;
代码:
#include<iostream>
using namespace std;
class BaseClass
{
public:
BaseClass
{
Number=90;
cout<<"constructor of BaseClass!"<<endl;
}
~BaseClass
{cout<<"destructor of BaseClass!"<<endl;}
private:
int Number;
};
class DerivedClass:public BaseClass
{
public:
DerivedClass
{
cout<<"constrctor of DerivedClass!"<<endl;
}
~DerivedClass
{
cout<<"destructor of DerivedClass!"<<endl;
}
};
int main
{
DerivedClass der;
return 0;
}
执行结果:
3、分析:(1)执行Base得构造函数;
(2)执行Derived得对象obj得Base类构造函数,并将obj(5)中参数5赋值给X及Derived类构造函数;
(3)执行Derived类得对象obj得Derived得析取函数、在执行Derived类得obj得Base析取函数,最后执行与第一步相对应得Base得析取函数;
执行结果:
4、虚基类:使得在继承间接共同基类时只保留一份成员。
若不使用虚基类,在最终得派生类中会保留该间接共同基类数据成员得多份同名成员。
代码:
#include<iostream>
using namespace std;
class vehicle
{
public:
vehicle(float m,float w)
{
MaxSpeed=m;Weight=w;
}
~vehicle{}
void run
{
cout<<"running of vehicle!"<<endl;
}
void stop
{
cout<<"stopping of vehicle!"<<endl;
}
float MaxSpeed;
float Weight;
};
class bicycle:virtual public vehicle
{
public:
bicycle(float m,float w,float h):vehicle(m,w)
{
Height=h;
}
~bicycle{}
float Height;
};
class motorcar:virtual public vehicle
{
public:
motorcar(float m,float w,int s):vehicle(m,w)
{
SeatNum=s;
}
~motorcar{}
int SeatNum;
};
class motorcycle:public bicycle,public motorcar
{
public:
motorcycle(float m,float w,float h,int s):vehicle(m,w),bicycle(m,w,h),motorcar(m,w,s){}
~motorcycle{}
void display
{
cout<<"MaxSpeed="<<MaxSpeed<<endl;
cout<<"Weight="<<Weight<<endl;
cout<<"Height="<<Height<<endl;
cout<<"SeatNum="<<SeatNum<<endl;
}
};
void main
{
float m,w,h;
int s;
cout<<"please input \nMaxSpeed=";
cin>>m;
cout<<"Weight=";
cin>>w;
cout<<"Height=";
cin>>h;
cout<<"SeatNum=";
cin>>s;
motorcycle moc(m,w,h,s);
moc、display;
}
运行结果:
5、代码:
#include<iostream>
#include<string>
using namespace std;
class People
{
public:
People(string n,string s,string b,string i)
{
number=n;
sex=s;
birthday=b;
id=i;
};
~People{}
protected:
string number;
string sex;
string birthday;
string id;
};
class Student:virtual public People
{
public:
Student(string n,string s,string b,string i,string c):People(n,s,b,i)
{
classNo=c;
}
~Student{}
protected:
string classNo;
};
class Teacher:virtual public People
{
public:
Teacher(string n,string s,string b,string i,string p,string d):People(n,s,b,i)
{
principalship=p;
department=d;
}
~Teacher{}
protected:
string principalship;//职务
string department;//部门
};
class Graduate:public Student
{
public:
Graduate(string n,string s,string b,string i,string c,string su,string t):People(n,s,b,i),Student(n,s,b,i,c)
{
subject=su;
teacher_adviser=t;
}
~Graduate{}
protected:
string subject;//专业
string teacher_adviser;//导师
};
class TA:public Graduate,public Teacher
{
public:
TA(string n,string s,string b,string i,string c,string su,string t,string p,string d):People(n,s,b,i),Graduate(n,s,b,i,c,su,t),Teacher(n,s,b,i,p,d)
{}
~TA{}
void display
{
cout<<"编号: "<<number<<endl;
cout<<"性别: "<<sex<<endl;
cout<<"生日: "<<birthday<<endl;
cout<<"身份证号: "<<id<<endl;
cout<<"班级: "<<classNo<<endl;
cout<<"专业: "<<subject<<endl;
cout<<"导师: "<<teacher_adviser<<endl;
cout<<"导师职务: "<<principalship<<endl;
cout<<"导师部门: "<<department<<endl;
}
};
void main
{
string n,s,b,i,c,su,t,p,d;
cout<<"请输入编号:"<<endl;cin>>n;
cout<<"请输入性别:"<<endl;cin>>s;
cout<<"请输入生日:"<<endl;cin>>b;
cout<<"请输入身份证号:"<<endl;cin>>i;
cout<<"请输入班级:"<<endl;cin>>c;
cout<<"请输入专业:"<<endl;cin>>su;
cout<<"请输入导师:"<<endl;cin>>t;
cout<<"请输入导师职务:"<<endl;cin>>p;
cout<<"请输入导师部门:"<<endl;cin>>d;
TA ta(n,s,b,i,c,su,t,p,d);
ta、display;
}
运行结果:

四、实验总结:
在本次操作中,前四个题操作较顺利,在做第五题时,调试改正了好久,(1)在多次派生后得初始化时,不懂得对基类进行初始化,导致编译错误;(2)在定义性别,身份证号等时,将其定义为字符型,导致输出时,全乱码,后将其改成字符串形式,输出正确;虽然在后面将其改成字符串形式输出正确,但还就是不太清楚,若用字符型,怎样才能保证不乱码,字符串与字符数组,在什么情况下,如何选择更恰当,这就是后面急需解决得问题。