다형성

//--- 기준 클래스
class CShape
  {
protected: 
   int            m_type;                // 쉐이프 유형
   int            m_xpos;                // X - 기준점 좌표
   int            m_ypos;                // Y - 기준점 좌표
public:
   void           CShape(){m_type=0;};   // 구성자, type=0
   int            GetType(){return(m_type);};// 쉐이프 유형 반환
virtual
   double         GetArea(){return (0); }// 쉐이프 영역 반환
  };

//--- 파생 클래스 써클
class CCircle : public CShape            // 콜론 뒤에 기준 클래스를 정의합니다
  {                                      // 상속할 수 있는
private:
   double         m_radius;              // 원 반지름
 
public:
   void           CCircle(){m_type=1;};  // 구성자, type=1 
   void           SetRadius(double r){m_radius=r;};
   virtual double GetArea(){return (3.14*m_radius*m_radius);}// 써클 영역
  };

//--- 파생 클래스 사각형
class CSquare : public CShape            // 콜론 뒤에 기준 클래스를 정의합니다
  {                                      // 상속할 수 있는
private:
   double          m_square_side;        // 사각형 면
 
public:
   void            CSquare(){m_type=2;}; // constructor, type=1
   void            SetSide(double s){m_square_side=s;};
   virtual double  GetArea(){return (m_square_side*m_square_side);}// 사각형 면적
  };

//+------------------------------------------------------------------+
//| 스크립트 프로그램 시작 함수                                    |
//+------------------------------------------------------------------+
void OnStart()
  {
//--- 기준 유형의 개체 포인터 배열을 선언
   CShape *shapes[5];   // CShape 개체에 대한 포인터 배열
 
//--- 여기서 배열을 파생 객체로 채움
//--- CCircle 유형의 개체에 대한 포인터를 선언
   CCircle *circle=new CCircle();
//--- 원형 포인터에서 객체 특성 설정
   circle.SetRadius(2.5);
//--- 포인터 값을 shapes[0]에 배치
   shapes[0]=circle;
 
//--- 다른 CCircle 객체를 만들고 포인터를 shapes[1]에 기록
   circle=new CCircle();
   shapes[1]=circle;
   circle.SetRadius(5);
 
//--- 여기서는 shapes[2]에 대한 값을 설정하기 위해 의도적으로 "잊음"
//circle=new CCircle();
//circle.SetRadius(10);
//shapes[2]=circle;
 
//--- 사용되지 않는 요소에 대해 NULL 설정
   shapes[2]=NULL;
 
//--- CSquare 개체를 만들고 해당 포인터를 shapes[3]에 기록
   CSquare *square=new CSquare();
   square.SetSide(5);
   shapes[3]=square;
 
//--- CSquare 개체를 만들고 해당 포인터를 shapes[4]에 기록
   square=new CSquare();
   square.SetSide(10);
   shapes[4]=square;
 
//--- 포인터가 여러 개 있는데 크기를 파악해야 합니다
   int total=ArraySize(shapes);
//--- 배열의 모든 포인터를 통해 루프를 전달
   for(int i=0; i<5;i++)
     {
      //--- 지정된 인덱스의 포인터가 유효한 경우
      if(CheckPointer(shapes[i])!=POINTER_INVALID)
        {
         //--- 쉐이프의 유형 및 사각형 기록
         PrintFormat("%d 유형의 객체가 %G 정사각형을 갖습니다.",
               shapes[i].GetType(),
               shapes[i].GetArea());
        }
      //--- 포인터가 POINTER_INVALID 유형이 있는 경우
      else
        {
         //--- 오류 통지
         PrintFormat("객체 shapes[%d]이(가) 초기화되지 않았습니다! 포인트는 %s 입니다",
                     i,EnumToString(CheckPointer(shapes[i])));
        }
    }
 
//--- 생성된 모든 동적 개체를 삭제해야 합니다
   for(int i=0;i<total;i++)
     {
      //--- POINTER_DYNAMIC 유형의 포인터가 있는 개체만 삭제할 수 있습니다.
      if(CheckPointer(shapes[i])==POINTER_DYNAMIC)
        {
         //--- 삭제 통지
         PrintFormat("shapes[%d] 삭제",i);
         //--- 포인터로 객체 삭제
         delete shapes[i];
        }
    }
  }