设计模式之享元模式，C++实现
享元模式很常见，是一种减小内存的方式，大到三维场景中的一个房子，小到文字处理系统中的一个英文字母，都可以使用享元模式。
借鉴一下《大话设计模式》中的uml图吧
下面是代码：
// Flyweight.cpp : 定义控制台应用程序的入口点。//#include "stdafx.h"#include <Windows.h>#include <vector>#include <string>using namespace std;// 享元模式（Flyweight）。运用共享技术有效地支持大量细粒度的对象。// 假设场景// 某个三维游戏场景，有一片森林，准备用一棵树，通过摆放位置不同，// 缩放，角度不同的三棵树摆出一整片森林。// 时间关系，先不写析构部分了class Obj{public:Obj(const string &str): m_strName(str){}virtual void PrintInfo() {;}protected:string m_strName;};// 模型几何信息class Mesh : public Obj{public:Mesh(const string &str): Obj(str){}void PrintInfo(){string str = "Mesh information of " + m_strName;printf(str.c_str());}};// 模型渲染信息class RenderObject : public Obj{public:RenderObject(const string &str): Obj(str){}void PrintInfo(){string str = "Render information " + m_strName;printf(str.c_str());}};// 模型类class Model : public Obj{public:Model(const string &strName): Obj(strName), m_pMesh(new Mesh( strName)), m_pRO(new RenderObject(strName)){}virtual void PrintInfo(){;}protected:Mesh*m_pMesh;RenderObject*m_pRO;};// 模型姿态信息,其实每个模型都有自己的姿态// 现在假设只有模型树的姿态是需要自己设置的class POSInfo{public:POSInfo(double centerX, double centerY, double centerZ,double yaw,double pitch,double roll,double xScale, double yScale,double zScale): m_x(centerX), m_y(centerY), m_z(centerZ){//.....}double m_x;doublem_y;doublem_z;};// 模型树类class TreeModel : public Model{public:TreeModel(const string &strName): Model(strName), m_pInfo(new POSInfo(0,0,0,0,0,0,1,1,1)){}~TreeModel(){//only need to delete pos info}void CreateNewInstacne(POSInfo *pInfo){m_pInfo = pInfo;}void PrintInfo(){printf("\n.........\n");m_pMesh->PrintInfo();m_pRO->PrintInfo();printf(m_strName.c_str());printf(" : \ndetail information :\nx:%lf, y:%lf, z:%lf",m_pInfo->m_x, m_pInfo->m_y, m_pInfo->m_z);printf("\n.........\n");}protected:stringm_strName;POSInfo*m_pInfo;};class TreeModelFactory{public:TreeModelFactory(){TreeModel *pTM1 = new TreeModel("大树");TreeModel *pTM2 = new TreeModel("小树");TreeModel *pTM3 = new TreeModel("小小树");m_TreeModelVec.push_back(pTM1);m_TreeModelVec.push_back(pTM2);m_TreeModelVec.push_back(pTM3);}TreeModel* GetTreeInstance(int num){if (num >= 0 && num <= 2){return m_TreeModelVec[num];}return NULL;}~TreeModelFactory(){// .......// delete tree// delete mesh// delete ro}private:vector<TreeModel*> m_TreeModelVec;};int _tmain(int argc, _TCHAR* argv[]){TreeModelFactory *pTreeFactory = new TreeModelFactory();TreeModel* pT1 = pTreeFactory->GetTreeInstance(0);pT1->CreateNewInstacne(new POSInfo(1, 2,3,0,0,0,1,2,3));pT1->PrintInfo();TreeModel *pT2 = pTreeFactory->GetTreeInstance(2);pT2->CreateNewInstacne(new POSInfo(6, 2,3,7,0,0,1,2,3));pT2->PrintInfo();TreeModel *pT3 = pTreeFactory->GetTreeInstance(2);pT3->CreateNewInstacne(new POSInfo(10, 12,30,7,0,0,1,2,3));pT3->PrintInfo();// ...// ...// 这样森林中所有的树只有三种几何体和渲染体，比较节省内存// // 当然，如果要给每一个不同的树一个序号或者要保存每一颗树的信息，可以加一个TreeInstance类// TreeIns包含序号，位置指针和treeModel的指针即可// 如果不需要保存这些信息，那么只需要保存PosInfo列表// 需要的时候再进行组合（CreateNewInstacne），然后打印信息return 0;}输出结果
.........
Mesh information of 大树Render information 大树 :
detail information :
x:1.000000, y:2.000000, z:3.000000
.........
.........
Mesh information of 小小树Render information 小小树 :
detail information :
x:6.000000, y:2.000000, z:3.000000
.........
.........
Mesh information of 小小树Render information 小小树 :
detail information :
x:10.000000, y:12.000000, z:30.000000
.........
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