Type: Structural Flyweight: 避免大量拥有相同内容的小类的开销(如耗费内存)，使大家共享一个类(元类)。找出这些对象群的共同点,设计一个元类，封装可以被共享的类。另外，还有一些特性是取决于应用(context)，是不可共享的，这也Flyweight中两个重要概念内部状态intrinsic和外部状态extrinsic之分。
#include <iostream>
#include <map>
using namespace std;
#define State int
class Flyweight
{
public:
virtual void operation(State extrinsicState) = 0;
};
class ConcreteFlyweight: public Flyweight
{
public:
ConcreteFlyweight(State key):intrinsicState(key){};
void operation(State extrinsicState)
{
cout<<"ConcreteFlyweight intrinsicState:"<<intrinsicState
<<" extrinsicState"<<extrinsicState<<endl;
};
private:
State intrinsicState;
};
class UnsharedConcreteFlyweight: public Flyweight
{
public:
void operation(State extrinsicState)
{
cout<<"UnsharedConcreteFlyweight"<<endl;
};
private:
State allState;
};
class FlyweightFactory
{
public:
Flyweight* getFlyweight(State key)
{
Flyweight* pFlyweight = m_Flyweights[key];
if(pFlyweight == NULL)
{
pFlyweight = new ConcreteFlyweight(key);
m_Flyweights[key] = pFlyweight;
}
return pFlyweight;
};
private:
map<State, Flyweight*> m_Flyweights;
};
int main()
{
FlyweightFactory flyweightfactory;
flyweightfactory.getFlyweight(0)->operation(0);
flyweightfactory.getFlyweight(1)->operation(0);
system("pause");
return 0;
}
