C++模式-FlyWeight

意图：
运用共享技术有效地支持大量细粒度的对象
适用：
一个应用程序使用了大量的对象
完全由于使用大量的对象，造成很大的存储开销
对象的大多数状态都可变为外部状态
如果删除对象的外部状态，那么可以用相对较少的共享对象取代很多组对象
UML

解析：
Flywweight模式大量使用在当一些可以被共享的对象经常使用的情况下

//test.h

#include <string>

#include <list>

//////////////////////////////////////////////////////////////////////////

using namespace std;

class Flyweight

{

public:

virtual ~Flyweight(){}

string GetIntrinsicState();

virtual void Operation(string& ExtrinsicState) = 0;

protected:

Flyweight(const string& state) : m_state(state){}

private:

string m_state;

};

class FlyweightFactory

{

public:

FlyweightFactory(){}

~FlyweightFactory();

Flyweight* GetFlyweight(const string& key);

private:

list<Flyweight*> m_listFlyweight;

};

class ConCreateFlyweight : public Flyweight

{

public:

ConCreateFlyweight(const string& state) : Flyweight(state){}

virtual ~ConCreateFlyweight(){}

virtual void Operation(string& ExtrinsicState);

};

// test.cpp : Defines the entry point for the console application.

#include "stdafx.h"

#include <iostream>

#include "test.h"

using namespace std;

//////////////////////////////////////////////////////////////////////////

inline string Flyweight::GetIntrinsicState()

{

return m_state;

}

FlyweightFactory::~FlyweightFactory()

{

list<Flyweight*>::iterator iter1,iter2,temp;

for (iter1 = m_listFlyweight.begin(),iter2 = m_listFlyweight.end(); iter1 != iter2;)

{

temp = iter1;

++iter1;

delete(*temp);

}

m_listFlyweight.clear();

}

Flyweight* FlyweightFactory::GetFlyweight(const string& key)

{

list<Flyweight*>::iterator iter1,iter2;

//查看列表中是否有存在的对象

for (iter1 = m_listFlyweight.begin(),iter2 = m_listFlyweight.end(); iter1 != iter2; ++iter1)

{

if ((*iter1)->GetIntrinsicState() == key)

{

cout <<"The Flyweight:"<<key<<"already exits"<<endl;

return (*iter1);

}

cout << "Creating a new Flyweight:"<<key<<endl;

Flyweight* pFlyweight = new ConCreateFlyweight(key);

m_listFlyweight.push_back(pFlyweight);

}

void ConCreateFlyweight::Operation(string& ExtrinsicState)

{

}

//////////////////////////////////////////////////////////////////////////

int main(int argc, char* argv[])

{

FlyweightFactory flyweightFactory;

flyweightFactory.GetFlyweight("hello");

flyweightFactory.GetFlyweight("world");

flyweightFactory.GetFlyweight("hello");

system("pause");

return 0;

}

posted on 2008-08-20 22:54 黑色天使阅读(457) 评论(0) 编辑收藏引用所属分类: 设计模式

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