클래스

클래스 기본

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

namespace CAR_CONST
{
	enum
	{
		ID_LEN = 20, MAX_SPD = 200, FUEL_STEP = 2, ACC_STEP = 10, BRK_STEP = 10
	};
}
class Car
{
private:
	char gamerID[CAR_CONST::ID_LEN];
	int fuelGauge;
	int curSpeed;
public:
	void InitMenbers(const char* ID, int fuel);
	void ShowCarState();
	void Accel();
	void Break();
};

void Car::InitMenbers(const char * ID, int fuel)
{
	strcpy(gamerID, ID);
	fuelGauge = fuel;
	curSpeed = 0;
}

void Car::ShowCarState()
{
	cout << "소유자ID: " << gamerID << endl;
	cout << "연료량: " << fuelGauge << endl;
	cout << "현재속도: " << curSpeed << "km/s" << endl << endl;
}

void Car::Accel()
{
	if (fuelGauge <= 0)
		return;
	else
		fuelGauge -= CAR_CONST::FUEL_STEP;

	if (curSpeed + CAR_CONST::ACC_STEP >= CAR_CONST::MAX_SPD)
	{
		curSpeed = CAR_CONST::MAX_SPD;
		return;
	}

	curSpeed += CAR_CONST::ACC_STEP;
}

void Car::Break()
{
	if (curSpeed < CAR_CONST::BRK_STEP)
	{
		curSpeed = 0;
		return;
	}

	curSpeed -= CAR_CONST::BRK_STEP;
}


int main()
{
	Car run99;
	run99.InitMenbers("run99",100);
	run99.Accel();
	run99.Accel();
	run99.ShowCarState();
	run99.Break();
	run99.ShowCarState();

	return 0;
}

---

private, public, protected

• private : 어디서든 접근허용
• public : 상속관계에 놓여있을 때, 유도 클래스에서의 접근허용
• protected : 클래스 내(클래스 내에 정의된 함수)에서만 접근허용

#include <iostream>
using namespace std;

class MyClass
{
private: // 외부 접근 (95%)X
	// 값은 멤버함수를 통해서만 초기화 가능
	int private_val;

public: // 외부 접근 O
	int public_val;

protected: // 상속에서만 접근 가능
	int protected_val;

public: // 멤버변수는 무조건 public
	void get()
	{
		cout << "private_val: " << private_val << endl;
		cout << "public_val: " << public_val << endl;
	}
	void set(int an)
	{
		private_val = an;
	}
};

int main()
{
	MyClass o;
	// o.private_val;
	o.public_val = 10;
	// o.protected_val;
	o.set(1);
	o.get();

	MyClass m;
	m.public_val = 20;
	m.set(2);
	m.get();

	return 0;
}

---

클래스 기반의 두 가지 객체생성 방법

1. 일반적인 변수의 선언방식

classname object;

2. 동적 할당방식(힙 할당 방식)

classname * ptrObj = new classname;

---

C++에서의 파일 분할

프로그램 실행 과정

• Car.h : 클래스의 선언 담기
• Car.cpp : 클래스의 정의(멤버함수의 정의) 담기

---

//39_Car.h
#pragma once
#ifndef __CAR_H__
#define __CAR_H__

namespace CAR_CONST
{
	enum
	{
		ID_LEN = 20, MAX_SPD = 200, FUEL_STEP = 2, ACC_STEP = 10, BRK_STEP = 10
	};
}

class Car
{
private:
	char gamerID[CAR_CONST::ID_LEN];
	int fuelGauge;
	int curSpeed;
public:
	void InitMenbers(const char* ID, int fuel);
	void ShowCarState();
	void Accel();
	void Break();
};

#endif // !__CAR_H__

---

//39_Car.cpp
#include <iostream>
#include <cstring>
#include"39_Car.h"
using namespace std;

void Car::InitMenbers(const char* ID, int fuel)
{
	strcpy(gamerID, ID);
	fuelGauge = fuel;
	curSpeed = 0;
}

void Car::ShowCarState()
{
	cout << "소유자ID: " << gamerID << endl;
	cout << "연료량: " << fuelGauge << endl;
	cout << "현재속도: " << curSpeed << "km/s" << endl << endl;
}

void Car::Accel()
{
	if (fuelGauge <= 0)
		return;
	else
		fuelGauge -= CAR_CONST::FUEL_STEP;

	if (curSpeed + CAR_CONST::ACC_STEP >= CAR_CONST::MAX_SPD)
	{
		curSpeed = CAR_CONST::MAX_SPD;
		return;
	}

	curSpeed += CAR_CONST::ACC_STEP;
}

void Car::Break()
{
	if (curSpeed < CAR_CONST::BRK_STEP)
	{
		curSpeed = 0;
		return;
	}

	curSpeed -= CAR_CONST::BRK_STEP;
}

---

//39_RacingMain.cpp
#include "39_Car.h"

int main()
{
	Car run99;
	run99.InitMenbers("run99", 100);
	run99.Accel();
	run99.Accel();
	run99.ShowCarState();
	run99.Break();
	run99.ShowCarState();

	return 0;
}

---

---

객체간의 대화

#include <iostream>
using namespace std;

class FruitSeller
{
private:
	int APPLE_PRICE;
	int numofApples;
	int myMoney;

public:
	void InitMenbers(int price, int num, int money)
	{
		APPLE_PRICE = price;
		numofApples = num;
		myMoney = money;
	}
	int SaleApples(int money)
	{
		int num = money / APPLE_PRICE;
		numofApples -= num;
		myMoney += money;
		return num;
	}
	void ShowSalesResult()
	{
		cout << "남은 사과: " << numofApples << endl;
		cout << "판매 수익: " << myMoney << endl << endl;
	}
};

class FruitBuyer
{
	int myMoney;
	int numofApples;

public:
	void InitMenbers(int money)
	{
		numofApples = 0;
		myMoney = money;
	}
	void BuyApples(FruitSeller& seller, int money)
	{
		numofApples += seller.SaleApples(money);
		myMoney -= money;
	}
	void ShowSalesResult()
	{
		cout << "현재 잔액: " << myMoney << endl;
		cout << "사과 개수: " << numofApples << endl << endl;
	}
};

int main()
{
	FruitSeller seller;
	seller.InitMenbers(1000, 20, 0);

	cout << "과일 판매자의 현황: " << endl;
	seller.ShowSalesResult();

	FruitBuyer buyer;
	buyer.InitMenbers(5000);
	buyer.BuyApples(seller, 2000);

	cout << "과일 판매자의 현황: " << endl;
	seller.ShowSalesResult();
	cout << "과일 구매자의 현황: " << endl;
	buyer.ShowSalesResult();

	return 0;
}