享元模式（Flyweight Pattern）是一種軟體設計模式。

 它使用共享物件，用來儘可能減少記憶體使用量以及分享資訊給儘可能多的相似物件；適合用於當大量物件只是重複因而導致無法令人接受的使用大量記憶體。

通常物件中的部分狀態是可以分享。常見做法是把它們放在外部資料結構，當需要使用時再將它們傳遞給享元。

享元模式通過共享的方式，高效的支援大量的細粒度的操作。

FlyweightPattern.h

#pragma once
#include<iostream>
#include<string>
#include<map>

class Person
{
public:
	Person(std::string name,int age):m_name_string(name),m_age_int(age) {};
	virtual ~Person() {};

	virtual void printT() = 0;
private:
	
protected:
	std::string m_name_string;
	int m_age_int;
};

class Teacher :public Person
{
public:
	Teacher(std::string name, int age, std::string id) :Person(name, age), m_id_string(id){};
	virtual ~Teacher() {};
	virtual void printT(){std::cout << "name:"<<m_name_string<<" age:"<<m_age_int<<" id:"<<m_id_string << std::endl;}
private:

protected:
	std::string m_id_string;
	
};

// 完成老師節點的儲存
class FlyweightTeacherFactory
{
public:
	FlyweightTeacherFactory()
	{
		m_teacherMap.clear();
	}
	~FlyweightTeacherFactory()
	{
		std::map<std::string, Person*>::iterator it;
		while (!m_teacherMap.empty())
		{
			it = m_teacherMap.begin();

			delete (it->second);

			m_teacherMap.erase(it);

		}
	}
	Person * getTeacher(std::string id)
	{
		
		std::map<std::string, Person*>::iterator it= m_teacherMap.find(id);
		if (it == m_teacherMap.end())
		{
			// 如果id不存在，建立新的物件，插曲map後返回
			std::string name;
			int age;
			std::cout << "請輸入姓名,年齡";
			std::cin >> name>>age;
			Teacher* teacher = new Teacher(name, age, id);
			// 新物件插入容器
			m_teacherMap.insert(std::pair<std::string,Person*>(id,teacher));
			return teacher;
		}
		else
		{
			// 如果id存在，直接返回查詢到的結果
			return it->second;
		}
			
		return nullptr;
	}
private:
	std::map<std::string, Person*> m_teacherMap;
protected:
};


class FlyweightPattern
{
public:
	FlyweightPattern() {};
	~FlyweightPattern() {};
};

 

FlyweightPattern.cpp

#include "FlyweightPattern.h"

mainTest.cpp

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


int main(void)
{
	FlyweightTeacherFactory* flyweightTeacherFactory = new FlyweightTeacherFactory;
	Teacher* teacher= dynamic_cast<Teacher*>(flyweightTeacherFactory->getTeacher("001"));
	teacher->printT();

	Teacher* teacher2 = dynamic_cast<Teacher*>(flyweightTeacherFactory->getTeacher("001"));
	teacher2->printT();

	delete teacher;
	delete teacher2;
	delete flyweightTeacherFactory;

	system("pause");
	return 0;
}