享元模式——C++实现

问题描述：

设计一个围棋软件，在系统中只存在一个白棋对象和一个黑棋对象，但是它们可以在棋盘的不同位置显示多次。

类图：

 

 代码：

#include<iostream>
using namespace std;
#include<String>
#include<vector>
//棋子颜色
enum ChessColor { BLACK, WHITE };
//棋子位置
struct Coordinates
{
    int x;
    int y;
    Coordinates(int a, int b) : x(a), y(b) {}
};
//棋子定义
class Chess
{
protected:
    ChessColor m_color; //颜色
public:
    Chess(ChessColor color) : m_color(color) {}
    ~Chess() {}
    virtual void Draw() {}
};
class BlackChess : public Chess
{
public:
    BlackChess(ChessColor color) : Chess(color) {}
    ~BlackChess() {}
    void Draw() {
        cout << "绘制一颗黑棋"<<endl;
    }
};
class WhiteChess : public Chess
{
public:
    WhiteChess(ChessColor color) : Chess(color) {}
    ~WhiteChess() {}
    void Draw() {
        cout << "绘制一颗白棋"<<endl;
    }
};
class ChessFactory
{
private:
    vector<Coordinates> m_vecPos; //存放棋子的位置
    Chess *m_blackChess;       //黑棋棋子
    Chess *m_whiteChess;       //白棋棋子
    string m_blackName;
    string m_whiteName;
public:
    ChessFactory(string black, string white) : m_blackName(black), m_whiteName(white)
    {
        m_blackChess = NULL;
        m_whiteChess = NULL;
    }
    ~ChessFactory() {
        delete m_blackChess;
        delete m_whiteChess;
    }
    void setChess(ChessColor color, Coordinates pos)
    {
        if (color == BLACK)
        {
            if (m_blackChess == NULL)
                m_blackChess = new BlackChess(color);
            cout << m_blackName << "在位置：" << pos.x << ',' << pos.y ;
            m_blackChess->Draw();
        }
        else
        {
            if (m_whiteChess == NULL)
                m_whiteChess = new WhiteChess(color);
            cout << m_whiteName << "的位置：" << pos.x << ',' << pos.y ;
            m_whiteChess->Draw();
        }
        m_vecPos.push_back(pos);
    }
};
//主函数
int main()
{
    ChessFactory chessFactory("甲", "乙");
    chessFactory.setChess(BLACK, Coordinates(2, 3));
    chessFactory.setChess(WHITE, Coordinates(3, 6));
    chessFactory.setChess(BLACK, Coordinates(5, 2));
    chessFactory.setChess(WHITE, Coordinates(4, 3));
    chessFactory.setChess(BLACK, Coordinates(3, 7));
}

　　运行截图：