友元和运算符重载
题设
类体
C++代码实现
Student.h文件
class Student
{
private:
char *m_pcSno;
char *m_pcSname;
int m_nScore;
//how to store the string ?
public:
Student(char *pcSno,char *pcSname,int nScore);
~Student();
Student& operator=(int Score);
friend void display(const Student &stu);
};
Student.cpp文件
#include <iostream>
#include <string.h>
#include "Student.h"
using namespace std;
Student::Student(char *pcSno,char *pcSname,int nScore)
{
// the stirng is stored in the static area,
//so dont need to create an area to store the string
m_pcSname = new char[strlen(pcSname) + 1];
strcpy(m_pcSname,pcSname);
m_pcSno = new char[strlen(pcSno) + 1];
strcpy(m_pcSno,pcSno);
m_nScore = nScore;
}
Student::~Student()
{
delete []m_pcSname;
delete []m_pcSno;
cout<<"deleting"<<endl;
}
Student& Student::operator=(int Score)
{
m_nScore = Score;
return *this;
}
- main函数测试文件
#include <iostream>
#include "Student.h"
using namespace std;
int main()
{
Student s("YC1710011","zhangninig",90);
display(s);
s = 93;
display(s);
return 0;
}
void display(const Student &stu)
{
cout<<"name:"<<stu.m_pcSname<<endl;
cout<<"no:"<<stu.m_pcSno<<endl;
cout<<"score:"<<stu.m_nScore<<endl;
}
分析总结
- 注意，对于字符串的处理，传入的是字符串，在函数体内部，要申请特定长度的空间用来存储字符串，同时长度要在原长上加1
Student::Student(char *pcSno,char *pcSname,int nScore)
{
m_pcSname = new char[strlen(pcSname) + 1];
//比原长要长一个单位，保存‘\0’
strcpy(m_pcSname,pcSname);
//采用strcpy函数来进行复制
m_pcSno = new char[strlen(pcSno) + 1];
strcpy(m_pcSno,pcSno);
m_nScore = nScore;
}
静态成员和多文件结构
题设
C++代码实现
Cube.h文件
class Cube
{
private:
double side;
static int totalNumber;
public:
Cube();
Cube(double s);
~Cube();
double getVolume();
int getTotalNumber();
void SetSide(double s);
};
Cube.cpp文件
#include <iostream>
#include "Cube.h"
using namespace std;
int Cube::totalNumber = 0;
Cube::Cube()
{
totalNumber ++;
side = 0;
}
Cube::Cube(double s)
{
totalNumber ++;
side = s;
}
Cube::~Cube()
{
totalNumber --;
cout<<"deleting!"<<endl;
}
double Cube::getVolume()
{
return side * side * side;
}
int Cube::getTotalNumber()
{
cout<<"the total number of the cube is "<<totalNumber<<endl;
}
void Cube::SetSide(double s)
{
side = s;
}
main测试文件
#include <iostream>
#include "Cube.h"
using namespace std;
int main()
{
Cube c1(4),c2;
cout<<c1.getVolume()<<endl;
c2.SetSide(7);
cout<<c2.getVolume()<<endl;
c2.getTotalNumber();
return 0;
}
分析与总结
- 对于totalNumber的静态变量，用来统计的整个类体的对象的数目的，在对象的构造函数中要存在，同样的在析构函数也要存在，确保数据动态变化。
Cube::Cube()
{
totalNumber ++;
//及时更新的静态数据
side = 0;
}
Cube::Cube(double s)
{
totalNumber ++;
//及时更新动态数据
side = s;
}
Cube::~Cube()
{
totalNumber --;
//及时更新动态数据
cout<<"deleting!"<<endl;
}
- 关于静态数据成员的使用
- 在类体内部进行声明，需要关键字static
- 在类体外定义，不需要用static关键字
对象成员
题设
类体描述
Point类
Circle类
C++实现
DefineClass.h文件
class Point1
{
private:
int m_nX;
int m_nY;
public:
Point1 (int nX,int nY);
~Point1();
friend class Circle;
};
class Circle
{
private:
Point1 m_pointCenter;
int m_nR;
public:
Circle(int nX,int nY,int nR);
~Circle();
void displayInfo();
};
DefineClass.cpp文件
Point1::~Point1()
{
cout<<"ddeleting the point!"<<endl;
}
Circle::Circle(int nX,int nY,int nR):m_pointCenter(nX,nY)
{
m_nR = nR;
cout<<"constructing the circle"<<endl;
}
//how to organize the member of the object
Circle::~Circle()
{
cout<<"deleting the circle!"<<endl;
}
void Circle::displayInfo()
{
cout<<"the cneter is :"<<m_pointCenter.m_nX<<" "
<<m_pointCenter.m_nY<<endl;
cout<<"the height is :"<<m_nR<<endl;
}
main测试文件
#include <iostream>
#include "DefineClass.h"
using namespace std;
int main()
{
Circle c(10,15,5);
c.displayInfo();
return 0;
}
分析与总结
- 对象的成员的初始化方式，直接在参数声明列表的后续进行的声明，在函数体中不需要再另外说明
Circle::Circle(int nX,int nY,int nR):m_pointCenter(nX,nY)
{
m_nR = nR;
cout<<"constructing the circle"<<endl;
}
- 作为类的友好类，可以访问另一类中的所有成员函数，包括私有成员。A可以访问B中的所有的资源
