设计模式之享元模式(FlyWeight)

#include <iostream>

#include <string>

#include <list>

#include <vector>

using namespace std;

enum COLOR{WHITE,BLACK};



/************************************************************************/

/* 装饰模式的作用是为对象增加属性										*/

/************************************************************************/



struct PiecePos

{

	int x;

	int y;

	PiecePos(int a,int b):x(a),y(b){}

};



class Piece

{

public:

	virtual void draw(){}

};

class BlackPiece:public Piece

{

public:

	virtual void draw(){cout << " set a black piece"<<endl;}

};

class WhitePiece:public Piece

{

public:

	virtual void draw(){cout << " set a white piece"<<endl;}

};





class PieceBoard

{

public:

	PieceBoard(string balckname,string whitename):

	m_whitename(whitename),m_balckname(balckname),m_blackpiece(NULL),m_whitepiece(NULL)

	{



	}

	void SetPiece(COLOR color,PiecePos pos)

	{

		if (color == BLACK)

		{

			if (NULL == m_blackpiece)

			{

				m_blackpiece = new BlackPiece();

			}

			cout << m_balckname << " on the pos" << pos.x << " and " << pos.y;

			m_blackpiece->draw();

		}

		else

		{

			if (NULL == m_whitepiece)

			{

				m_whitepiece = new WhitePiece();

			}

			cout << m_whitename << " on the pos" << pos.x << " and " << pos.y;

			m_whitepiece->draw();

		}

		m_vecPos.push_back(pos);

	}

private:

	vector<PiecePos> m_vecPos;

	Piece *m_blackpiece;

	Piece *m_whitepiece;

	string m_balckname;

	string m_whitename;

};





int main()

{

	PieceBoard pieceboard("A","B");

	pieceboard.SetPiece(WHITE,PiecePos(4,6));	

	pieceboard.SetPiece(BLACK,PiecePos(3,5));

	pieceboard.SetPiece(WHITE,PiecePos(2,8));

	pieceboard.SetPiece(BLACK,PiecePos(1,9));

	return 0;

}

 

享元模式原理：所谓享元模式，是共享一些元数据对象，例如棋盘的棋子，如果我们对每个棋子建立一个对象然后组织成一个容器，则需要很多个对象。可以只建立两个对象，一个黑子对象，一个白子对象，由棋盘共享，棋盘维护一个保存棋子位置的对象。

代码如下：