5. 복사 생성자(윤성우 열혈강의 C++ 예제코드)

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출처: 윤성우 열혈강의 C++ 예제코드

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5.1. ‘복사 생성자’와의 첫 만남

• 복사 생성자 직접 선언하기

#include <iostream>
using namespace std;

class SoSimple
{
private:
	int num1;
	int num2;
public:
	SoSimple(int n1, int n2) 
		: num1(n1), num2(n2)
	{
		// empty
	}

	SoSimple(const SoSimple &copy)
		: num1(copy.num1), num2(copy.num2)
	{
		cout<<"Called SoSimple(SoSimple &copy)"<<endl;
	}

	void ShowSimpleData()
	{
		cout<<num1<<endl;
		cout<<num2<<endl;
	}
};

int main(void)
{
	SoSimple sim1(15, 30);
	cout<<"생성 및 초기화 직전"<<endl;
	SoSimple sim2=sim1;
	cout<<"생성 및 초기화 직후"<<endl;
	sim2.ShowSimpleData();
	return 0;
}

• explicit 키워드로 대입연산자에서의 복사생성자 호출막기

explicit SoSimple(const SoSimple &copy)
	: num1(copy.num1), num2(copy.num2)
{
	cout<<"Called SoSimple(SoSimple &copy)"<<endl;
}

5.2. ‘깊은 복사’와 ‘얕은 복사’

• shallow copy

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

class Person
{
	char * name;
	int age;
public:
	Person(char * myname, int myage)
	{
		int len=strlen(myname)+1;
		name=new char[len];
		strcpy(name, myname);
		age=myage;
	}
	void ShowPersonInfo() const
	{
		cout<<"이름: "<<name<<endl;
		cout<<"나이: "<<age<<endl;
	}
	~Person()
	{
		delete []name;
		cout<<"called destructor!"<<endl;
	}
};

int main(void)
{
	Person man1("Lee dong woo", 29);
	Person man2=man1;
	man1.ShowPersonInfo();
	man2.ShowPersonInfo();
	return 0;
}

이름: Lee dong woo
나이: 29
이름: Lee dong woo
나이: 29
called destructor!

• deep copy

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

class Person
{
	char * name;
	int age;
public:
	Person(const Person &copy) 
		: age(copy.age)
	{
		name = new char[strlen(copy.name) + 1];
		strcpy(name, copy.name);
	}
	Person(char * myname, int myage)
	{
		int len = strlen(myname) + 1;
		name = new char[len];
		strcpy(name, myname);
		age = myage;
	}
	void ShowPersonInfo() const
	{
		cout << "이름: " << name << endl;
		cout << "나이: " << age << endl;
	}
	~Person()
	{
		delete[]name;
		cout << "called destructor!" << endl;
	}
};

int main(void)
{
	Person man1("Lee dong woo", 29);
	Person man2 = man1;
	man1.ShowPersonInfo();
	man2.ShowPersonInfo();
	return 0;
}

이름: Lee dong woo
나이: 29
이름: Lee dong woo
나이: 29
called destructor!
called destructor!

5.3. 복사 생성자의 호출시점

• 기존에 생성된 객체를 이용해서 새로운 객체를 초기화

Person man1("Lee dong woo", 29);
Person main2 = main1;

• 매개변수 전달시점의 호출

#include <iostream>
using namespace std;

class SoSimple
{
private:
	int num;
public:
	SoSimple(int n) : num(n)
	{  }
	SoSimple(const SoSimple& copy) : num(copy.num)
	{
		cout<<"Called SoSimple(const SoSimple& copy)"<<endl;
	}
	void ShowData()
	{
		cout<<"num: "<<num<<endl;
	}
};
	
void SimpleFuncObj(SoSimple ob)
{
	ob.ShowData();
}

int main(void)
{
	SoSimple obj(7);
	cout<<"함수호출 전"<<endl;
	SimpleFuncObj(obj);
	cout<<"함수호출 후"<<endl;
	return 0;
}

• 결과값 반환시의 호출

#include <iostream>
using namespace std;

class SoSimple
{
private:
	int num;
public:
	SoSimple(int n) : num(n)
	{ }
	SoSimple(const SoSimple& copy) : num(copy.num)
	{
		cout<<"Called SoSimple(const SoSimple& copy)"<<endl;
	}
	SoSimple& AddNum(int n)
	{
		num+=n;
		return *this;
	}
	void ShowData()
	{
		cout<<"num: "<<num<<endl;
	}
};

SoSimple SimpleFuncObj(SoSimple ob)
{
	cout<<"return 이전"<<endl;
	return ob;
}

int main(void)
{
	SoSimple obj(7);
	SimpleFuncObj(obj).AddNum(30).ShowData();
	obj.ShowData();
	return 0;
}

• 임시객체의 소멸시점 확인

#include <iostream>
using namespace std;

class SoSimple
{
private:
	int num;
public:
	SoSimple(int n) : num(n)
	{ }
	SoSimple(const SoSimple& copy) : num(copy.num)
	{
		cout<<"Called SoSimple(const SoSimple& copy)"<<endl;
	}
	SoSimple& AddNum(int n)
	{
		num+=n;
		return *this;
	}
	void ShowData()
	{
		cout<<"num: "<<num<<endl;
	}
};

SoSimple SimpleFuncObj(SoSimple ob)
{
	cout<<"return 이전"<<endl;
	return ob;
}

int main(void)
{
	SoSimple obj(7);
	SimpleFuncObj(obj).AddNum(30).ShowData();
	obj.ShowData();
	return 0;
}

New Object: 0039F7EC
New Copy obj: 0039F6D0
Parm ADR: 0039F6D0
New Copy obj: 0039F708
Destroy obj: 0039F6D0
Destroy obj: 0039F708

New Copy obj: 0039F6D0
Parm ADR: 0039F6D0
New Copy obj: 0039F7E0
Destroy obj: 0039F6D0
Return Obj 0039F7E0
Destroy obj: 0039F7E0
Destroy obj: 0039F7EC