9. 가상(Virtual)의 원리와 다중상속

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출처: 윤성우 열혈강의 C++ 예제코드

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9.1. 멤버함수와 가상함수의 동작원리

• 오버라이딩 시점에 따른 가상함수 호출

#include <iostream>
using namespace std;

class AAA
{
private:
	int num1;
public:
	virtual void Func1() { cout<<"Func1"<<endl; }
	virtual void Func2() { cout<<"Func2"<<endl; }	
};

class BBB: public AAA
{
private:
	int num2;
public:
	virtual void Func1() { cout<<"BBB::Func1"<<endl; }
	void Func3() { cout<<"Func3"<<endl; }
};

int main(void)
{
	AAA * aptr=new AAA();
	aptr->Func1();

	BBB * bptr=new BBB();
	bptr->Func1();
	return 0;
}

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9.2. 다중상속(Multiple Inheritance)에 대한 이해

• 가상상속을 이용하여 중복상속 피하기

#include <iostream>
using namespace std;

class Base
{
public:
	Base() { cout<<"Base Constructor"<<endl; }
	void SimpleFunc() { cout<<"BaseOne"<<endl; }
};

class MiddleDrivedOne : virtual public Base
{
public:
	MiddleDrivedOne() : Base()
	{
		cout<<"MiddleDrivedOne Constructor"<<endl; 
	} 
	void MiddleFuncOne() 
	{ 
		SimpleFunc();
		cout<<"MiddleDrivedOne"<<endl; 
	}
};

class MiddleDrivedTwo : virtual public Base
{
public:
	MiddleDrivedTwo() : Base()
	{
		cout<<"MiddleDrivedTwo Constructor"<<endl; 
	} 
	void MiddleFuncTwo() 
	{ 
		SimpleFunc();
		cout<<"MiddleDrivedTwo"<<endl; 
	}
};

class LastDerived : public MiddleDrivedOne, public MiddleDrivedTwo
{
public:
	LastDerived() : MiddleDrivedOne(), MiddleDrivedTwo()
	{
		cout<<"LastDerived Constructor"<<endl; 
	}
	void ComplexFunc()
	{
		MiddleFuncOne();
		MiddleFuncTwo();
		SimpleFunc();
	}
};

int main(void)
{
	cout<<"객체생성 전 ..... "<<endl;
	LastDerived ldr;
	cout<<"객체생성 후 ..... "<<endl;
	ldr.ComplexFunc();
	return 0;
}