设计模式之享元模式

英文：Flyweight模式

#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 m_intrinsicState;
};

#include "Flyweight.h"


Flyweight::Flyweight(std::string intrinsicState)
{
    this->m_intrinsicState = intrinsicState;
}


Flyweight::~Flyweight()
{
}

void Flyweight::Operation(const std::string &extrinsicState)
{

}

std::string Flyweight::GetIntrinsicState()
{
    return this->m_intrinsicState;
}

 

#pragma once
#include "Flyweight.h"
class ConcreateFlyweight :
    public Flyweight
{
public:
    ConcreateFlyweight(std::string intrinsicState);
    ~ConcreateFlyweight();

    void Operation(const std::string &extrinsicState);
};

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


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:IN[" << this->GetIntrinsicState() << "]OUT[" << extrinsicState << "]" << std::endl;
}

 

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

class FlyweightFactory
{
public:
    FlyweightFactory();
    ~FlyweightFactory();

    Flyweight *GetFlyweight(const std::string &key);

private:
    std::vector<Flyweight *> m_vec_FW;
};

#include "FlyweightFactory.h"
#include "ConcreateFlyweight.h"
#include <iostream>


FlyweightFactory::FlyweightFactory()
{
}


FlyweightFactory::~FlyweightFactory()
{
    for (std::vector<Flyweight *>::iterator it = m_vec_FW.begin(); it < m_vec_FW.end(); it++)
    {
        delete *it;
        *it = NULL;
    }
    m_vec_FW.clear();
}

Flyweight *FlyweightFactory::GetFlyweight(const std::string &key)
{
    std::vector<Flyweight *>::iterator it = m_vec_FW.begin();
    for (; it != m_vec_FW.end(); it++)
    {
        if ((*it)->GetIntrinsicState() == key)
        {
            std::cout << "already created by user..." << std::endl;
            return *it;
        }
    }

    Flyweight *fw = new ConcreateFlyweight(key);
    m_vec_FW.push_back(fw);
    return fw;
}

 

测试

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

int main()
{
    FlyweightFactory *fc = new FlyweightFactory();

    Flyweight *fw1 = fc->GetFlyweight("hello");

    Flyweight *fw2 = fc->GetFlyweight("world!");

    Flyweight *fw3 = fc->GetFlyweight("hello");

    if (fc)
    {
        delete fc;
        fc = NULL;
    }
    std::cout << "Hello World!\n"; 
}