享元模式-c++

#include <iostream>
#include <string>
#include <vector>

using namespace std;
//棋子颜色
enum PieceColor { BLACK, WHITE };
//棋子位置
struct PiecePos
{
    int x;
    int y;
    PiecePos(int a, int b) : x(a), y(b) {}
};
//棋子定义
class Piece
{
protected:
    PieceColor m_color; //颜色
public:
    Piece(PieceColor color) : m_color(color) {}
    ~Piece() {}
    virtual void Draw() {}
};
class BlackPiece : public Piece
{
public:
    BlackPiece(PieceColor color) : Piece(color) {}
    ~BlackPiece() {}
    void Draw() { cout << "绘制一颗黑棋\n"; }
};
class WhitePiece : public Piece
{
public:
    WhitePiece(PieceColor color) : Piece(color) {}
    ~WhitePiece() {}
    void Draw() { cout << "绘制一颗白棋\n"; }
};

class PieceBoard
{
private:
    vector<PiecePos> m_vecPos; //存放棋子的位置
    Piece* m_blackPiece;       //黑棋棋子 
    Piece* m_whitePiece;       //白棋棋子
    string m_blackName;
    string m_whiteName;
public:
    PieceBoard(string black, string white) : m_blackName(black), m_whiteName(white)
    {
        m_blackPiece = NULL;
        m_whitePiece = NULL;
    }
    ~PieceBoard() { delete m_blackPiece; delete m_whitePiece; }
    void SetPiece(PieceColor color, PiecePos pos)
    {
        if (color == BLACK)
        {
            if (m_blackPiece == NULL)  //只有一颗黑棋
                m_blackPiece = new BlackPiece(color);
            cout << m_blackName << "在位置(" << pos.x << ',' << pos.y << ")";
            m_blackPiece->Draw();
        }
        else
        {
            if (m_whitePiece == NULL)
                m_whitePiece = new WhitePiece(color);
            cout << m_whiteName << "在位置(" << pos.x << ',' << pos.y << ")";
            m_whitePiece->Draw();
        }
        m_vecPos.push_back(pos);
    }
};


int main()
{
    PieceBoard pieceBoard("A", "B");
    pieceBoard.SetPiece(BLACK, PiecePos(4, 4));
    pieceBoard.SetPiece(WHITE, PiecePos(4, 16));
    pieceBoard.SetPiece(BLACK, PiecePos(16, 4));
    pieceBoard.SetPiece(WHITE, PiecePos(16, 16));

    return 0;
}