열혈C++ CH06

PP.249 MyFriendClass.cpp

//Boy.h
#ifndef __BOY_H__
#define __BOY_H__
#include "Girl.h"

class Boy
{
private:
    int height;
    friend class Girl; // Girl클래스에 대한 friend 선언
public:
    Boy(int len);
    void ShowYourFriendInfo(Girl& frn);
};

#endif // !__BOY_H__

//Boy.cpp

#include <iostream>
#include <cstring>
#include "Boy.h"
using namespace std;

Boy::Boy(int len) : height(len) {}

void Boy::ShowYourFriendInfo(Girl& frn)
{
    cout << "소녀의 전화번호 : " << frn.phoneNum << endl;
}

//Girl.h
#ifndef __GIRL_H__
#define __GIRL_H__
#include "Boy.h"

class Girl
{
private:
    char phoneNum[20];
    friend class Boy; // Boy클래스에 대한 friend 선언
public:
    Girl(const char* phnum);
    void ShowYourFriendInfo(Boy& frn);  
};

#endif // !__GIRL_H__

//Girl.cpp
#include <iostream>
#include <cstring>
#include "Girl.h"
using namespace std;

Girl::Girl(const char* phnum)
{
    strcpy(phoneNum, phnum);
}
 
void Girl::ShowYourFriendInfo(Boy& frn)
{
    cout << "소년의 키 : " << frn.height << "cm" << endl;
}

// main.cpp
#include <iostream>
#include <cstring>
#include "Boy.h"
#include "Girl.h"
using namespace std;

int main()
{
    Boy boy(170);
    Girl girl("010-123-4567");
    boy.ShowYourFriendInfo(girl);
    girl.ShowYourFriendInfo(boy);
    return 0;
}

PP. 252 MyFriendFunction.cpp

#include <iostream>
#include <cstring>
using namespace std;

class Point;

class PointOP 
{
private:
    int opcnt;
public:
    PointOP(): opcnt(0) {}
    Point PointAdd(const Point&, const Point&);
    Point PointSub(const Point&, const Point&);
    ~PointOP() 
    {
        cout << "동작 회수 : " << opcnt << endl;
    }
};

class Point 
{
private:
    int x;
    int y;
public:
    Point(const int& xpos, const int& ypos) : x(xpos), y(ypos) {}
    friend Point PointOP::PointAdd(const Point&, const Point&);
    friend Point PointOP::PointSub(const Point&, const Point&);
    friend void ShowPointPos(const Point&);
};

Point PointOP::PointAdd(const Point& pt1, const Point& pt2)
{
    opcnt++;
    return Point(pt1.x + pt2.x, pt1.y + pt2.y);
}
Point PointOP::PointSub(const Point& pt1, const Point& pt2)
{
    opcnt++;
    return Point(pt1.x - pt2.x, pt1.y - pt2.y);
}

int main()
{
    Point pos1(1, 2);
    Point pos2(3, 4);
    PointOP op;
    ShowPointPos(op.PointAdd(pos1, pos2));
    ShowPointPos(op.PointSub(pos1, pos2));
    return 0;
}

void ShowPointPos(const Point& pos) 
{
    cout << "x : " << pos.x << endl;
    cout << "y : " << pos.y << endl;
}