【初学设计模式】Flyweight (享元)

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类图：

 

 

 

 

 

 

代码实现：

 

类声明：

/********************************************************************File: flyweight.hAuthor:blackboy [e-mail]:享元模式Created:2011-03-17Modified:2011-03-17 10:40*********************************************************************/// Client负责维护一个Flyweight*指针列表，此列表的索引与FlyweightContext的索引一一对应。// Client就是通过这种一一对应的关系来查询某个Flyweight的状态的。// 注意，在Flyweight*列表中往下遍历时，调用FlyweightContext::Next()。#ifndef __FLYWEIGHT_H__#define __FLYWEIGHT_H__#include <vector>#include <string>namespace blackboycpp{ typedef std::string State; #define STATE_A "STATE_A" #define STATE_B "STATE_B" #define STATE_C "STATE_C" #define STATE_NULL "NULL" #define POOL_SIZE 5 class FlyweightContext; ////////////////////////////////////////////////////////////////////////// class Flyweight { public: virtual void Operation(FlyweightContext&); }; class ConcreteFlyweight : public Flyweight { public: virtual void Operation(FlyweightContext&); }; class UnsharedConcreteFlyweight : public Flyweight { public: virtual void Operation(FlyweightContext&); }; ////////////////////////////////////////////////////////////////////////// class FlyweightContext { public: FlyweightContext(); State GetState(); void AddState(State); void Rewind(); void Next(); private: int _index; std::vector<State> _states; }; ////////////////////////////////////////////////////////////////////////// // 可共享Flyweight由Factory负责删除，不共享Flyweight由Client删除。 class FlyweightFactory { public: FlyweightFactory(); ~FlyweightFactory(); ConcreteFlyweight* CreateFlyweight(int key); UnsharedConcreteFlyweight* CreateUnsharedFlyweight(); private: std::vector<ConcreteFlyweight*> _flyweightPool; };}#endif

 

 

 

类实现：

#include <iostream>#include "flyweight.h"namespace blackboycpp{ ////////////////////////////////////////////////////////////////////////// void Flyweight::Operation(FlyweightContext& context) { std::cout << "Flyweight::Operation(FlyweightContext&) + " << context.GetState() << std::endl; } void ConcreteFlyweight::Operation(FlyweightContext& context) { std::cout << "ConcreteFlyweight::Operation(FlyweightContext&) + " << context.GetState() << std::endl; } void UnsharedConcreteFlyweight::Operation(FlyweightContext& context) { std::cout << "UnsharedConcreteFlyweight::Operation(FlyweightContext&) + " << context.GetState() << std::endl; } ////////////////////////////////////////////////////////////////////////// FlyweightContext::FlyweightContext() { _index = 0; } State FlyweightContext::GetState() { std::cout << "FlyweightContext::GetState()/n"; if(_index < (int)_states.size()) { return _states[_index]; } return STATE_NULL; } void FlyweightContext::AddState(State s) { std::cout << "FlyweightContext::AddState(State)/n"; _states.push_back(s); } void FlyweightContext::Next() { std::cout << "FlyweightContext::Next()/n"; _index++; } void FlyweightContext::Rewind() { std::cout << "FlyweightContext::Rewind()/n"; _index = 0; } ////////////////////////////////////////////////////////////////////////// FlyweightFactory::FlyweightFactory() { for (int i=0; i<POOL_SIZE; ++i) { ConcreteFlyweight* p = new ConcreteFlyweight; _flyweightPool.push_back(p); } } FlyweightFactory::~FlyweightFactory() { for(std::vector<ConcreteFlyweight*>::iterator i=_flyweightPool.begin(); i!=_flyweightPool.end(); ++i) { if(*i) { delete *i; *i = 0; } } } ConcreteFlyweight* FlyweightFactory::CreateFlyweight(int key) { std::cout << "FlyweightFactory::CreateFlyweight(int)/n"; if(key < (int)_flyweightPool.size()) { std::cout << "get Flyweight from pool/n"; return _flyweightPool[key]; } else { std::cout << "new Flyweight/n"; ConcreteFlyweight* p = new ConcreteFlyweight; _flyweightPool.push_back(p); return p; } } UnsharedConcreteFlyweight* FlyweightFactory::CreateUnsharedFlyweight() { std::cout << "FlyweightFactory::CreateUnsharedFlyweight()/n"; return new UnsharedConcreteFlyweight; }}

 

 

 

main()：

#include <cstdlib>#include "flyweight.h"using namespace blackboycpp;int main(int argc, char** argv){ std::vector<Flyweight*> flyweights; FlyweightFactory* factory = new FlyweightFactory; FlyweightContext* context = new FlyweightContext; Flyweight* p = factory->CreateFlyweight(1); flyweights.push_back(p); context->AddState(STATE_A); Flyweight* p2 = factory->CreateFlyweight(2); flyweights.push_back(p2); context->AddState(STATE_B); Flyweight* p3 = factory->CreateUnsharedFlyweight(); flyweights.push_back(p3); context->AddState(STATE_NULL); Flyweight* p4 = factory->CreateFlyweight(POOL_SIZE+2); flyweights.push_back(p4); context->AddState(STATE_C); for(std::vector<Flyweight*>::iterator i=flyweights.begin(); i!=flyweights.end(); ++i) { (*i)->Operation(*context); context->Next(); } delete p3; delete factory; system("pause"); return 0;}