C++享元模式詳解
#include <iostream> #include <list> #include <map> using namespace std; enum class EnumColor //棋子類型 { 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) {} //構造函數 }; /*棋子類*/ class Piece { public: //構造函數 Piece(EnumColor tmpcolor, Position tmppos) :m_color(tmpcolor), m_pos(tmppos){} //棋子的繪制 void draw() { if(m_color == EnumColor::Black) { cout << "在位置:(" << m_pos.m_x << "," << m_pos.m_y << ")處繪制瞭一個黑色棋子!" << endl; } else { cout << "在位置:(" << m_pos.m_x << "," << m_pos.m_y << ")處繪制瞭一個白色棋子!" << endl; } } private: EnumColor m_color; //棋子顏色 Position m_pos; //棋子位置 }; int main() { //檢測內存泄漏 _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(); //釋放資源 delete p_piece1; delete p_piece2; delete p_piece3; delete p_piece4; return 0; }
對於上面的例程來說,棋子的類型無非就是兩種,黑和白,在實際的下棋過程當中,隻有位置是不一樣的,但是卻衍生出瞭多個具有相似度的對象,我們能否進行改造一下,比如,對象隻有兩個,黑和白,在實際的運轉的時候,改變他們的位置就可以瞭,這樣就不用new很多給相似的對象出來瞭。下面我們進行改造一下。引入享元模式。
#include <iostream> #include <list> #include <map> using namespace std; enum EnumColor //棋子類型 { 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) {} //構造函數 }; class Piece //棋子抽象類 { 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 << ")處繪制瞭一個黑色棋子!" << 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 << ")處繪制瞭一個白色棋子!" << endl; } }; class pieceFactory //創建棋子的工廠 { public: virtual ~pieceFactory() { //釋放內存 for(auto iter = m_FlyWeightMap.begin(); iter != m_FlyWeightMap.end(); ++iter) { Piece* tmpfw = iter->second; delete tmpfw; } m_FlyWeightMap.clear(); } //獲取享元對象,也就是獲取被共享的棋子對象 Piece* getFlyWeight(EnumColor tmpcolor) { auto iter = m_FlyWeightMap.find(tmpcolor); if(iter == m_FlyWeightMap.end()) { //沒有該享元對象,那麼就創建出來 Piece* tmpfw = nullptr; if(tmpcolor == Black) //黑子 { tmpfw = new BlackPiece(); } else //白子 { tmpfw = new WhitePiece(); } //以棋子顏色枚舉值作為key,增加條目到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容器來保存所有的享元對象,一共就兩個享元對象(黑色棋子一個,白色棋子一個) }; int main() { //檢測內存泄漏 _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 //釋放資源 delete pfactory; return 0; }
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