在开发时，假设创建非常多对象，就会造成非常大的内存开销。特别是大量轻量级（细粒度）的对象，还会造成内存碎片。

Flyweight模式就是运用共享技术，有效支持大量细粒度对象的设计模式。

其类结构图例如以下：

在FlyweightFactory中有一个管理、存储对象的对象池，当调用GetFlyweight时会首先遍历对象池。假设已存在。则返回，否则创建新对象加入到对象池中。

有些对象可能不想被共享，那么就使用UnshareConcreteFlyweight。

实现:
//Flyweight.h

//Flywight.h#ifndef _FLYWEIGHT_H_
#define _FLYWEIGHT_H_
#include<string>
using std::string;class Flyweight
{
public:virtual ~Flyweight();virtual void Operation(const string& extrinsicState);string GetIntrinsicState();
protected:Flyweight(string intrinsicState);
private:string _intrinsicState;
};class ConcreteFlyweight :public Flyweight
{
public:ConcreteFlyweight(string intrinsicState);~ConcreteFlyweight();void Operation(const string& extrinsicState);
};
#endif

//Flyweight.cpp

//Flyweight.cpp#include"Flyweight.h"
#include<iostream>
using std::cout;Flyweight::Flyweight(string intrinsicState)
{_intrinsicState = intrinsicState;
}
Flyweight::~Flyweight()
{}
void Flyweight::Operation(const string& extrinsicState)
{}
string Flyweight::GetIntrinsicState()
{return _intrinsicState;
}ConcreteFlyweight::ConcreteFlyweight(string intrinsicState) :Flyweight(intrinsicState)
{cout << "ConcreteFlyweight Build..." << std::endl;
}
ConcreteFlyweight::~ConcreteFlyweight()
{}
void ConcreteFlyweight::Operation(const string& extrinsicState)
{cout << "ConcreteFlyweight:内蕴[" << this->GetIntrinsicState() << "]外蕴[" << extrinsicState << "]" << std::endl;
}

//FlyweightFactory.h

//FlyweightFactory.h#ifndef _FLYWEIGHTFACTORY_H_
#define _FLYWEIGHTFACTORY_H_#include"Flyweight.h"
#include<string>
#include<vector>
using std::string;
using std::vector;
class FlyweightFactory
{
public:FlyweightFactory();~FlyweightFactory();Flyweight* GetFlyweight(const string& key);
private:vector<Flyweight*> _fly;};
#endif

//FlyweightFactory.cpp

//FlyweightFactory.cpp#include"FlyweightFactory.h"
#include<iostream>
#include<string>
#include<cassert>
using std::string;
using std::cout;FlyweightFactory::FlyweightFactory()
{}
FlyweightFactory::~FlyweightFactory()
{}
Flyweight* FlyweightFactory::GetFlyweight(const string& key)
{vector<Flyweight*>::iterator it = _fly.begin();for (; it != _fly.end(); it++){if ((*it)->GetIntrinsicState() == key){cout << "already create by users..." << std::endl;return *it;}}Flyweight* fn = new ConcreteFlyweight(key);_fly.push_back(fn);return fn;
}

//main.cpp

#include"Flyweight.h"
#include"FlyweightFactory.h"
int main()
{FlyweightFactory* fc = new FlyweightFactory();Flyweight* fw1 = fc->GetFlyweight("hello");Flyweight* fw2 = fc->GetFlyweight("world");Flyweight* fw3 = fc->GetFlyweight("hello");return 0;
}