享元模式c++代码实现

享元--程序中会使用到大量的对象，这些对象耗费大量的内存，这些对象有相同的
地方(内部的状态)可以共享，可以用一个简单工厂类去返回已经存在的对象，不存
在的则创建，这些对象用一个容器存放。使用对象时可以再传入外部的状态。

 

// flyweight.cpp : 定义控制台应用程序的入口点。//#include <iostream>#include <map>#include <string>using namespace std;class Flyweight{public://map会使用空构造Flyweight(){}Flyweight(string intrinsicState){this->intrinsicState = intrinsicState;}virtual void operation(string extrinsicState){cout << "Flyweight::operation()" << endl;}string intrinsicState;};class ConcreteFlyweight:public Flyweight{public:ConcreteFlyweight(string intrinsicState):Flyweight(intrinsicState){}void operation(string extrinsicState){cout << "intrinsicState: " << this->intrinsicState << endl;cout << "extrinsicState: " << extrinsicState << endl;}};class FlyweightFactory{public://静态成员函数要使用静态成员static FlyweightFactory *getInstance(){if(f == NULL){f = new FlyweightFactory();}return f;}Flyweight * getFlyweight(string intrinsicState){if(1 != m.count(intrinsicState)){//要使用多态，这里要放指针,放对象不行m[intrinsicState] = new ConcreteFlyweight(intrinsicState);}return m[intrinsicState];}~FlyweightFactory(){cout << "~FlyweightFactory" << endl;//new的内存要释放if(!m.empty()){map<string,Flyweight *>::iterator it = m.begin();while(it != m.end()){cout << it->first << endl;delete it->second;it++;}}/* 这个代码要注释掉，因为main中的fc与这里的f指的是相同的内存，在delete时，先调用析构函数，会释放一遍内存，完了delete还要再释放一遍if(NULL != f){delete f;f = NULL;}*/}protected:FlyweightFactory(){f = NULL;m.clear();}static FlyweightFactory *f;map<string,Flyweight*> m;};//静态成员初始化FlyweightFactory * FlyweightFactory::f = NULL;int main(){FlyweightFactory *fc = FlyweightFactory::getInstance();Flyweight *f1 = fc->getFlyweight("f1");Flyweight *f2 = fc->getFlyweight("f2");Flyweight *f3 = fc->getFlyweight("f1");f1->operation("o1");f2->operation("o2");f3->operation("o3");delete fc;return 0;}