class Coordinate

{

public:

Coordinate(int x,int y);

~Coordinate();

void setX(int x);

//const修饰后只具有只读权限所以可以修饰get函数

//相当于 int getX(const Coordinate *this);

int getX() const;

//而set函数具有写权限所以不能用const（不能修改函数里面的值）修饰

void setY(int y);

int getY() const;

private:

int m_iX;

int m_iY;

};

#include "Coordinate.h"

#include <iostream>

using namespace std;

Coordinate::Coordinate(int x, int y)

{

m_iX = x;

m_iY = y;

cout << "Coordinate() " << m_iX << "," << m_iY << endl;

}

Coordinate::~Coordinate()

{

cout << "~Coordinate() " << m_iX << "," << m_iY << endl;

}

void Coordinate::setX(int x)

{

m_iX = x;

}

int Coordinate::getX() const

{

return m_iX;

}

void Coordinate::setY(int y)

{

m_iY = y;

}

int Coordinate::getY() const

{

return m_iY;

}

#include "Coordinate.h"

class Line

{

public:

Line(int x1,int y1,int x2,int y2);

~Line();

void setA(int x, int y);

void setB(int x, int y);

//常成员函数注意：const和括号之间要隔开一个空格不然有些编译器下可能无法通过

//相当于 void printInfo(const Coordinate *this);

//也就是说常成员函数的const实际上修饰的是this指针使之成为常this指针

void printInfo() const;

// void printInfo(Coordinate *this); 隐藏的this指针

//同名的普通成员函数和常成员函数互为重载

void printInfo();

private:

const Coordinate m_coorA;//一个常对象成员

Coordinate m_coorB; //一个对象成员

};

#include "Line.h"

#include <iostream>

using namespace std;

Line::Line(int x1, int y1, int x2, int y2) :m_coorA(x1, y1), m_coorB(x2, y2)

{

cout << "Line()" << endl;

}

Line::~Line()

{

cout << "~Line()" << endl;

}

void Line::setA(int x, int y)

{

//m_coorA是常对象成员无法使用普通成员函数使用导致报错

//因为：setX(int x); 相当于 setX(Coordinate *this,int x);

//传进去的是m_coorA的常this指针（只读）m_coorA是个只具有读权限的对象

//而原函数里的this既有读权限又有写权限

//

//m_coorA.setX(x);

//m_coorA.setY(y);

}

void Line::setB(int x, int y)

{

m_coorB.setX(x);

m_coorB.setY(y);

}

void Line::printInfo() const

{

cout << "printInfo() const" << endl;

cout << "(" << m_coorA.getX() << "," << m_coorA.getY() << ")" << endl;

cout << "(" << m_coorB.getX() << "," << m_coorB.getY() << ")" << endl;

}

void Line::printInfo()

{

cout << "printInfo()" << endl;

cout << "(" << m_coorA.getX() << "," << m_coorA.getY() << ")" << endl;

cout << "(" << m_coorB.getX() << "," << m_coorB.getY() << ")" << endl;

}

#include <stdlib.h>

#include "Line.h"

using namespace std;

int main(void)

{

Line line1(1, 2, 3, 4);

line1.printInfo();//调用的是不带const的printInfo()

const Line line2(5, 6, 7, 8);

line2.printInfo();//调用的是带const的printInfo()

system("pause");

return 0;

}

//即常对象和常对象成员只能调用常成员函数

//而普通的对象和对象成员却可以调用普通成员函数和常成员函数

//

//常数据成员和常对象成员必须使用初始化列表初始化

//（即const修饰的数据成员和对象成员在构造函数中只能用初始化列表初始化）

//同名的普通成员函数和常成员函数互为重载