自己写的用c++实现的简单装饰者模式

在上传代码之前，先交代一下装饰模式的概念。。。

装饰模式（Decorator）可以在运行时动态地给对象增加功能。它也是对对象的包装，但与适配器模式不同的是它并没有改变被包装对象的接口，只是改变了它的能力范围，而且可以递归组合。

通过生成子类的方式也可以为对象增加功能，但它是静态的，而且大量的功能组合很容易产生“子类爆炸”现象。装饰模式可以动态、透明地给对象增加职责，并且在不需要的时候很容易去除，使用派生子类的方式无法达到这种灵活程度。

GOOD:当你向旧的类中添加新代码时，一般是为了添加核心职责或主要行为。而当需要加入的仅仅是一些特定情况下才会执行的特定的功能时（简单点就是不是核心应用的功能），就会增加类的复杂度。装饰模式就是把要添加的附加功能分别放在单独的类中，并让这个类包含它要装饰的对象，当需要执行时，客户端就可以有选择地、按顺序地使用装饰功能包装对象。

下面是主要实现，参照Head First的星巴兹咖啡案例实现。

#pragma once#include <boost/format.hpp>#include <iostream>#include <string>using namespace std;class CBeverage{public:CBeverage(void);~CBeverage(void);public:virtual int cost() = 0;virtual string getDescription(){return m_description;}virtual void setDescription(string strDescription){m_description = strDescription;}protected:string m_description;};class Blend: public CBeverage{public:int cost(){return 10;}};class DarkRoast: public CBeverage{public:int cost(){return 12;}};class Decorator: public CBeverage{public://virtual string getDescription();int cost(){return m_observed_->cost() + 0;}void setObserver(boost::shared_ptr<CBeverage> observed) { m_observed_ = observed; }protected:boost::shared_ptr<CBeverage> getobersver(){return m_observed_;}private:boost::shared_ptr<CBeverage> m_observed_;};class Milk: public Decorator{public:string getDescription(){return getobersver()->getDescription() + ", Milk";}int cost(){return getobersver()->cost() + 2;//milk price:2}};class Mocha: public Decorator{public:string getDescription(){return getobersver()->getDescription() + ", Mocha";}int cost(){return getobersver()->cost() + 3;//mocha price: 3}};class Whip: public Decorator{public:string getDescription(){return getobersver()->getDescription() + ", Whip";}int cost(){return getobersver()->cost() + 4;//whip price:4}};int _tmain(int argc, _TCHAR* argv[]){boost::shared_ptr<CBeverage> blendObserved(new Blend);blendObserved->setDescription("blend coffee");boost::shared_ptr<CBeverage> darkroastObers(new DarkRoast);darkroastObers->setDescription("DarkRoast coffee");boost::shared_ptr<Decorator> blendwithmilk(new Milk);blendwithmilk->setObserver(blendObserved);boost::shared_ptr<Decorator> blendwithmocha(new Mocha);blendwithmocha->setObserver(blendObserved);boost::shared_ptr<Decorator> darkroastwithmocha(new Mocha);darkroastwithmocha->setObserver(darkroastObers);boost::shared_ptr<Decorator> blendwithmochawhip(new Whip);blendwithmochawhip->setObserver(blendwithmocha);boost::shared_ptr<Decorator> blendwithmochawhipmilk(new Milk);blendwithmochawhipmilk->setObserver(blendwithmochawhip);cout<<blendwithmilk->cost()<<endl;cout<<blendwithmilk->getDescription()<<endl;cout<<blendwithmocha->cost()<<endl;cout<<blendwithmocha->getDescription()<<endl;cout<<darkroastwithmocha->cost()<<endl;cout<<darkroastwithmocha->getDescription()<<endl;cout<<blendwithmochawhip->cost()<<endl;cout<<blendwithmochawhip->getDescription()<<endl;cout<<blendwithmochawhipmilk->cost()<<endl;cout<<blendwithmochawhipmilk->getDescription()<<endl;return 0;}