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：

 

C++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));
}

　　

运行结果：