设计模式之享元模式(Flyweight)

优点：1)大幅度地降低内存中对象的数量

#include <iostream>#include <vector>using namespace std;class FlyWeight{public:    virtual ~FlyWeight(){}    string getInstrinsicState(){return _state;}    virtual void Operation(string &state) = 0;protected:    FlyWeight(const string &state){_state = state;}private:    string _state;};class ConcreateFlyweight : public FlyWeight{public:    ConcreateFlyweight(const string &state):FlyWeight(state){}    virtual ~ConcreateFlyweight(){}    virtual void Operation(string &state){cout << "ConcreateFlyweight:" << state.data() << endl;}};class FlyWeightFactory{public:    FlyWeightFactory(){}    ~FlyWeightFactory()    {        for(int i = 0; i < _vector.size(); ++i)            delete _vector.at(i);        _vector.clear();    }    FlyWeight *getFlyWeight(const string&key)    {        for(int i = 0; i < _vector.size(); ++i)        {            string state = _vector.at(i)->getInstrinsicState();            if(!strcmp(state.data(),key.data()))            {                cout << "The Flyweight:" << key.data() << " already exists" << endl;                return _vector.at(i);            }        }        std::cout << "Creating a new Flyweight:" << key.data() << std::endl;        FlyWeight *flyWeight = new ConcreateFlyweight(key);        _vector.push_back(flyWeight);        return flyWeight;    }private:    vector<FlyWeight *> _vector;};int main(){    FlyWeightFactory flyWeightFactory;    FlyWeight *f1 = flyWeightFactory.getFlyWeight("hello");    FlyWeight *f2 = flyWeightFactory.getFlyWeight("world");    flyWeightFactory.getFlyWeight("hello");    return 0;}

运行结果：
Creating a new Flyweight:hello
Creating a new Flyweight:world
The Flyweight:hello already exists