c++设计模式之享元模式

享元模式

定义：享元模式（FlyWeight），运用共享技术有效的支持大量细粒度的对象。

享元模式结构图：



兑现代码：

#include <iostream>
#include <string>
#include "map"
using namespace std;

class Person
{
public:
Person(string name,int age)
{
this->m_name=name;
this->m_age;
}
virtual void print()=0;
protected:
string m_name;
int m_age;
};
class Teacher:public Person
{
public:
Teacher(string name, int age,string id):Person(name,age)
{
this->m_id;
}
void print()
{
cout<<"name:"<<m_name<<"age:"<<m_age<<"id:"<<m_id<<endl;
}
private:
string m_id;
};

class FlyWeightTeacherFactory
{
public:
FlyWeightTeacherFactory()
{
map1.clear();
}
~FlyWeightTeacherFactory()
{
while(!map1.empty())
{
Person*tmp = NULL;
map<string,Person*>::iterator it = map1.begin();
tmp =it->second;
map1.erase(it);
delete tmp;
}
}

Person* GetTeacher(string id)
{
Person *tmp =NULL;
map<string,Person*>::iterator it;
it = map1.find(id);
if(it==map1.end())//没有找到,创建对象
{
string tmpname ;
int tmpage;
cout<<"\n请输入老师name:";
cin>>tmpname;
cout<<"\n请输入老师age:";
cin>>tmpage;
tmp = new Teacher(tmpname,tmpage,id);
map1.insert(pair<string,Person*>(id,tmp));
return  tmp;
}
else//有，这几返回此对象实例
{
tmp = it->second;
}
return tmp;
}
private:
map<string,Person*> map1;
};
void main()
{
Person *p1 =NULL;
Person *p2 =NULL;

FlyWeightTeacherFactory *fwtf = new FlyWeightTeacherFactory;
p1=fwtf->GetTeacher("001");
p2=fwtf->GetTeacher("001");

p1->print();
p2->print();
delete fwtf;

cout<<"nihao..."<<endl;
system("pause");
return ;
}

总结：

可以共享的对象，也就是说返回的同一类型的对象其实是同一实例，当客户端要求生成一个对象时，工厂会检测是否存在此对象的实例，如果存在那么直接返回此对象实例，如果不存在就创建一个实例并保存起来。通常工厂类会有一个集合类型的成员变量来用以保存对象，如map,hashtable,vector等。