C++享元模式详解 C++享元模式详解

总结

#include #include #include using namespace std; enum classEnumColor //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; }

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对于上面的例程来说，棋子的类型无非就是两种，黑和白，在实际的下棋过程当中，只有位置是不一样的，但是却衍生出了多个具有相似度的对象，我们能否进行改造一下，比如，对象只有两个，黑和白，在实际的运转的时候，改变他们的位置就可以了，这样就不用new很多给相似的对象出来了。下面我们进行改造一下。引入享元模式。

#include #include #include 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 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 deletepfactory; return 0; }