C++享元模式详解

#include <iostream>
#include <list>
#include <map>
using namespace std;

enum class  EnumColor //棋子类型
{
	Black, //黑
	White  //白
};
struct Position //棋子位置
{
	int m_x;
	int m_y;
	Position(int tmpx, int tmpy) :m_x(tmpx), m_y(tmpy) {} //构造函数			
};
/*棋子类*/
class Piece 
{
public:
	//构造函数
	Piece(EnumColor tmpcolor, Position tmppos) :m_color(tmpcolor), m_pos(tmppos){}
	//棋子的绘制
	void draw()
	{
		if(m_color == EnumColor::Black)
		{
			cout << "在位置：（" << m_pos.m_x << "，" << m_pos.m_y << "）处绘制了一个黑色棋子！" << endl;
		}
		else
		{
			cout << "在位置：（" << m_pos.m_x << "，" << m_pos.m_y << "）处绘制了一个白色棋子！" << endl;
		}
	}
private:
	EnumColor m_color; //棋子颜色
	Position m_pos; //棋子位置
};
int main()
{
	//检测内存泄漏
	_CrtSetDbgFlag(_CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF);
	Piece* p_piece1 = new Piece(EnumColor::Black, Position(3, 3)); //黑色落子到3,3位置
	p_piece1->draw();
	Piece* p_piece2 = new Piece(EnumColor::White, Position(5, 5)); //白色落子到5,5位置
	p_piece2->draw();
	Piece* p_piece3 = new Piece(EnumColor::Black, Position(4, 6)); //黑色落子到4,6位置
	p_piece3->draw();
	Piece* p_piece4 = new Piece(EnumColor::White, Position(5, 7)); //白色落子到5,7位置
	p_piece4->draw();
	//释放资源
	delete p_piece1;
	delete p_piece2;
	delete p_piece3;
	delete p_piece4;
	return 0;
}

#include <iostream>
#include <list>
#include <map>
using namespace std;

enum EnumColor //棋子类型
{
	Black, //黑
	White  //白
};
struct Position //棋子位置
{
	int m_x;
	int m_y;
	Position(int tmpx, int tmpy) :m_x(tmpx), m_y(tmpy) {} //构造函数			
};
class Piece //棋子抽象类
{
public:
	virtual ~Piece() {} 
public:
	virtual void draw(Position tmppos) = 0;
};

class BlackPiece :public Piece //黑色棋子
{
public:
	virtual void draw(Position tmppos)
	{
		cout << "在位置：（" << tmppos.m_x << "，" << tmppos.m_y << "）处绘制了一个黑色棋子！" << endl;
	}
};

class WhitePiece :public Piece //白色棋子
{
public:
	virtual void draw(Position tmppos)
	{
		cout << "在位置：（" << tmppos.m_x << "，" << tmppos.m_y << "）处绘制了一个白色棋子！" << endl;
	}
};

class pieceFactory //创建棋子的工厂
{
public:
	virtual ~pieceFactory()
	{
		//释放内存
		for(auto iter = m_FlyWeightMap.begin(); iter != m_FlyWeightMap.end(); ++iter)
		{
			Piece* tmpfw = iter->second;
			delete tmpfw;
		}
		m_FlyWeightMap.clear(); 
	}
	//获取享元对象，也就是获取被共享的棋子对象
	Piece* getFlyWeight(EnumColor tmpcolor)
	{
		auto iter = m_FlyWeightMap.find(tmpcolor);
		if(iter == m_FlyWeightMap.end())
		{
			//没有该享元对象，那么就创建出来
			Piece* tmpfw = nullptr;
			if(tmpcolor == Black) //黑子
			{
				tmpfw = new BlackPiece();
			}
			else //白子
			{
				tmpfw = new WhitePiece();
			}
			//以棋子颜色枚举值作为key，增加条目到map中
			m_FlyWeightMap.insert(make_pair(tmpcolor, tmpfw)); 
			return tmpfw;
		}
		else
		{
			return iter->second;
		}
	}
private:
	std::map<EnumColor, Piece*> m_FlyWeightMap; //享元池，用map容器来保存所有的享元对象，一共就两个享元对象（黑色棋子一个，白色棋子一个）
};
int main()
{
	//检测内存泄漏
	_CrtSetDbgFlag(_CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF);
	pieceFactory* pfactory = new pieceFactory();
	Piece* p_piece1 = pfactory->getFlyWeight(Black);
	p_piece1->draw(Position(3, 3));  //黑子落子到3,3位置
	Piece* p_piece2 = pfactory->getFlyWeight(White);
	p_piece2->draw(Position(5, 5));  //白子落子到5,5位置
	Piece* p_piece3 = pfactory->getFlyWeight(Black);
	p_piece3->draw(Position(4, 6));  //黑子落子到4,6位置
	Piece* p_piece4 = pfactory->getFlyWeight(White);
	p_piece4->draw(Position(5, 7));  //白子落子到5,7位置
	//释放资源
	delete  pfactory;
	return 0;
}