设计模式-结构型-装饰

#pragma once

#ifndef DECORATOR_H 

#define DECORATOR_H 

// 抽象基类,定义一个对象接口,可以为这个接口动态的添加职责. 
class Component 
{ 
public: 
  Component(){} 
  virtual ~Component(){} 

  // 纯虚函数,由派生类实现 
  virtual void Operation() = 0; 
}; 

// 抽象基类,维护一个指向Component对象的指针 
class Decorator : public Component 
{ 
public: 
  Decorator(Component* pComponent) 
    : m_pComponent(pComponent){} 
  virtual ~Decorator(); 

protected: 
    Component* m_pComponent; 
}; 

// 派生自Component,在这里表示需要给它动态添加职责的类 
class ConcreateComponent : public Component 
{ 
public: 
  ConcreateComponent(){} 
  virtual ~ConcreateComponent(){} 
  virtual void Operation(); 
}; 

// 派生自Decorator,这里代表为ConcreateComponent动态添加职责的类 
class ConcreateDecorator : public Decorator 
{ 
public: 
  ConcreateDecorator(Component* pComponent) 
    : Decorator(pComponent){} 
  virtual ~ConcreateDecorator(){} 
  virtual void Operation(); 

private: 
  void AddedBehavior(); 
}; 

#endif

#include "StdAfx.h"
#include "decorator_impl.h"

#include <iostream> 

Decorator::~Decorator() 
{ 
  delete m_pComponent; 
  m_pComponent = NULL; 
} 

void ConcreateComponent::Operation() 
{ 
  std::cout << "Operation of ConcreateComponent\n"; 
} 

void ConcreateDecorator::Operation() 
{ 
  m_pComponent->Operation(); //componet原有职责
  AddedBehavior(); //decorator动态添加职责
} 

void ConcreateDecorator::AddedBehavior() 
{ 
  std::cout << "AddedBehavior of ConcreateDecorator\n"; 
}

// Decorator.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include <stdlib.h>
#include <iostream>

#include "decorator_impl.h"

using namespace std;
//动态地给一个对象添加一些额外的职责。就增加功能来说，Decorator模式相比生成子类更为灵活
int _tmain(int argc, _TCHAR* argv[])
{
  // 初始化一个Component对象 
  Component* pComponent = new ConcreateComponent(); 
  // 采用这个Component对象去初始化一个Decorator对象, 
  cout<<"before decorator"<<endl;
  pComponent->Operation();
  cout<<endl;
  // 这样就可以为这个Component 对象动态添加职责 
  Decorator* pDecorator = new ConcreateDecorator(pComponent); 
  //Component* pDecorator = new ConcreateDecorator(pComponent); 
  cout<<"after decorator"<<endl;
  //对外表现为执行了component基本职责，并执行了decorator动态添加的职责
  pDecorator->Operation(); 
  
  delete pDecorator; 
  system("pause"); 

  return 0;
}