생성패턴-Factory Method

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[Factory Method]
의도:
객체를 생성하기 위해 인터페이스를 정의하지만, 어떤 클래스의 인스턴스를 생성할지에 대한
결정은 서브클래스에서 이루어지도록 Factory Method 패턴은 서브클래스에게 인스턴스 생성의
책임을 미룬다.

다른 이름:
Virtual Constructor
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/////////////////////////////////////////////////////////////////////////////
//
// A creational part of GoF's Design Patterns
//
// - Factory Method
//
/////////////////////////////////////////////////////////////////////////////
#include <windows.h>
#include <tchar.h>

#include <iostream>
#include <memory>

/////////////////////////////////////////////////////////////////////////////
//
// Product
//
//
/////////////////////////////////////////////////////////////////////////////
class Product
{
public:
 Product()          {}
 virtual ~Product() {}

public:
 virtual void Operation (void) = 0;
};

class ConcreteProductA : public Product
{
public:
 ConcreteProductA(){}
 virtual ~ConcreteProductA() {}

public:
 virtual void Operation (void)
 {
  std::cout << "ConcreteProductA::Operation()" << std::endl;
 }
};

class ConcreteProductB : public Product
{
public:
 ConcreteProductB(){}
 virtual ~ConcreteProductB() {}

public:
 virtual void Operation (void)
 {
  std::cout << "ConcreteProductB::Operation()" << std::endl;
 }
};

class ConcreteProductB_2 : public Product
{
public:
 ConcreteProductB_2(){}
 virtual ~ConcreteProductB_2() {}

public:
 virtual void Operation (void)
 {
  std::cout << "ConcreteProductB_2::Operation()" << std::endl;
 }
};

/////////////////////////////////////////////////////////////////////////////
//
// Factory Method
//
//
/////////////////////////////////////////////////////////////////////////////
enum ProductID
{
 Id_ConcreteProductA,
 Id_ConcreteProductB
};

class Createor
{
public:
 virtual ~Createor() {}

public:
 virtual std::auto_ptr<Product> Create (ProductID id)
 {
  if (Id_ConcreteProductA==id)
   return std::auto_ptr<Product> ( new ConcreteProductA() );

  if (Id_ConcreteProductB==id)
   return std::auto_ptr<Product> ( new ConcreteProductB() );

  return std::auto_ptr<Product>();
 }
};

class ConcreteCreateor : public Createor
{
public:
 virtual std::auto_ptr<Product> Create (ProductID id)
 {
  if (Id_ConcreteProductB==id)
   return std::auto_ptr<Product> ( new ConcreteProductB_2() );

  return Createor::Create(id);
 }
};

/////////////////////////////////////////////////////////////////////////////
//
// Startup
//
//
/////////////////////////////////////////////////////////////////////////////
int _tmain(int argc, _TCHAR* argv[])
{
 std::auto_ptr<Createor> c;
 std::auto_ptr<Product>  p;

 std::cout << "Created by Createor()" << std::endl;
 c.reset ( new Createor() );

 p = c->Create ( Id_ConcreteProductA );
 p->Operation ();

 p = c->Create ( Id_ConcreteProductB );
 p->Operation ();
 std::cout << std::endl;

 std::cout << "Created by ConcreteCreateor()" << std::endl;
 c.reset ( new ConcreteCreateor() );

 p = c->Create ( Id_ConcreteProductA );
 p->Operation ();

 p = c->Create ( Id_ConcreteProductB );
 p->Operation ();
 std::cout << std::endl;

 return 0;
}
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Created by Createor()
ConcreteProductA::Operation()
ConcreteProductB::Operation()

Created by ConcreteCreateor()
ConcreteProductA::Operation()
ConcreteProductB_2::Operation()