设计模式-FlyWeight(结构型模式) 针对 需要创建大量对象的情形，被共享的状态作为内部状态，不被共享的状态作为外部状态

以下代码来源： 设计模式精解－GoF 23种设计模式解析附C++实现源码

//Flyweight.h

#pragma once
#include<string>
class FlyWeight
{
public:
    virtual ~FlyWeight();
    virtual void Operation(const std::string & extrinsicState);
    std::string GetIntrinsicState();
protected:
    FlyWeight(std::string intrinsicState);
private:
    std::string _intrinsicState;
};

class ConcreateFlyWeight :public FlyWeight
{
public:
    ConcreateFlyWeight(std::string intrinsicState);
    ~ConcreateFlyWeight();
    void Operation(const std::string& extrinsicState);
protected:
private:
};

//Flyweight.cpp

#include"Flyweight.h"
#include<iostream>

FlyWeight::FlyWeight(std::string intrinsicState)
{
    this->_intrinsicState = intrinsicState;
}
FlyWeight::~FlyWeight(){}
void FlyWeight::Operation(const std::string& extrinsicState)
{

}
std::string FlyWeight::GetIntrinsicState()
{
    return this->_intrinsicState;
}
ConcreateFlyWeight::ConcreateFlyWeight(std::string intrinsicState) :FlyWeight(intrinsicState)
{
    std::cout << "ConcreateFlyWeight Build..." << intrinsicState << std::endl;
}
ConcreateFlyWeight::~ConcreateFlyWeight(){}
void ConcreateFlyWeight::Operation(const std::string& extrinsicState)
{
    std::cout << "ConcreateFlyWeight:内部[" << this->GetIntrinsicState() << "]外部[" << extrinsicState << "]" << std::endl;
}

//FlyWeightFactory.h

#pragma once

#include"Flyweight.h"
#include<vector>
#include<string>

class FlyWeightFactory
{
public:
    FlyWeightFactory();
    ~FlyWeightFactory();
    FlyWeight* GetFlyWeight(const std::string& key);
protected:
private:
    std::vector<FlyWeight*>_fly;
};

//FlyWeightFactory.cpp

#include"FlyWeightFactory.h"
#include<iostream>
#include<string>

FlyWeightFactory::FlyWeightFactory(){}
FlyWeightFactory::~FlyWeightFactory(){}
FlyWeight* FlyWeightFactory::GetFlyWeight(const std::string& key)
{
    for (std::vector<FlyWeight*>::iterator it = _fly.begin(); it != _fly.end(); ++it)
    {
        if ((*it)->GetIntrinsicState() == key)
        {
            std::cout << "Already created by users..." << std::endl;
            return *it;
        }
    }
    FlyWeight* fn = new ConcreateFlyWeight(key);
    _fly.push_back(fn);
    return fn;
}

//main.cpp

#include"Flyweight.h"
#include"FlyWeightFactory.h"
#include<string>
int main(int args, char* argv)
{
    FlyWeightFactory* flyfac = new FlyWeightFactory();
    FlyWeight* fw1 = flyfac->GetFlyWeight("Hello");
    FlyWeight* fw2 = flyfac->GetFlyWeight("World");
    FlyWeight* fw3 = flyfac->GetFlyWeight("Hello");
    getchar();
    return 0;

}