Decorator模式解决以下情况：我们需要为一个已经定义好的类添加新的职责（操作），通常的情况我们会定义一个新类继承自定义好的类，这样会带来一个问题。通过继承的方式解决这样的情况还带来了系统的复杂性，因为继承的深度会变得很深。而Decorator模式提供了一种给类增加职责的方法，不是通过继承实现，而是通过组合。
Decorator.h
//Decorator.h
#ifndef _DECORATOR_H_
#define _DECORATOR_H_
class Component
{
public:
virtual ~Component();
virtual void Operation();
protected:
Component();
private:
};
class ConcreteComponent:public Component
{
public:
ConcreteComponent();
~ConcreteComponent();
void Operation();
protected:
private:
};
class Decorator:public Component
{
public:
Decorator(Component* com);
virtual ~Decorator();
void Operation();
protected:
Component* _com;
private:
};
class ConcreteDecorator:public Decorator
{
public:
ConcreteDecorator(Component* com);
~ConcreteDecorator();
void Operation();
void AddedBehavior();
protected:
private:
};
#endif //~_DECORATOR_H_
Decorator.cpp
//Decorator.cpp
#include "Decorator.h"
#include <iostream>
Component::Component()
{
}
Component::~Component()
{
}
void Component::Operation()
{
}
ConcreteComponent::ConcreteComponent()
{
}
ConcreteComponent::~ConcreteComponent()
{
}
void ConcreteComponent::Operation()
{
std::cout<<"ConcreteComponent operation..."<<std::endl;
}
Decorator::Decorator(Component* com)
{
this->_com = com;
}
Decorator::~Decorator()
{
delete _com;
}
void Decorator::Operation()
{
}
ConcreteDecorator::ConcreteDecorator(Component* com):Decorator(com)
{
}
ConcreteDecorator::~ConcreteDecorator()
{
}
void ConcreteDecorator::AddedBehavior()
{
std::cout<<"ConcreteDecorator::AddedBehacior...."<<std::endl;
}
void ConcreteDecorator::Operation()
{
_com->Operation();
this->AddedBehavior();
}
main.cpp
#include "Decorator.h"
#include <iostream>
using namespace std;
int main(){
Component* com = new ConcreteComponent();
Decorator* dec = new ConcreteDecorator(com);
dec->Operation();
delete dec;
return 0;
}