设计模式读书笔记：Decorator（装饰）

2015-07-10 16:28:02

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意图：

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。

结构图：来自 《23种设计模式 - 郗晓勇》

实现：https://github.com/panshiqu/patterns/tree/master/Decorator

Component

namespace NS_DECORATOR {

class Component {
public:
	Component() {}
	virtual ~Component() {}
	virtual void operation(void) = 0;
};

} /* namespace NS_DECORATOR */

ConcreteComponent

#include "Component.h"
#include <iostream>

namespace NS_DECORATOR {

class ConcreteComponent : public Component
{
public:
	ConcreteComponent() {}
	virtual ~ConcreteComponent() {}
	virtual void operation(void)
	{
		std::cout << "ConcreteComponent" << std::endl;
	}
};

} /* namespace NS_DECORATOR */

Decorator

#include "Component.h"

namespace NS_DECORATOR {

class Decorator : public Component
{
public:
	Decorator(Component *component) : _component(component) {}
	virtual ~Decorator() {}
	virtual void operation(void)
	{
		_component->operation();
	}

private:
	Component *_component;
};

} /* namespace NS_DECORATOR */

ConcreteDecoratorA

#include "Decorator.h"
#include <iostream>

namespace NS_DECORATOR {

class ConcreteDecoratorA : public Decorator
{
public:
	ConcreteDecoratorA(Component *component) : Decorator(component) {}
	virtual ~ConcreteDecoratorA() {}
	virtual void operation(void)
	{
		Decorator::operation();
		addBehavior();
	}
	void addBehavior(void)
	{
		std::cout << "Jump" << std::endl;
	}
};

} /* namespace NS_DECORATOR */

ConcreteDecoratorB

#include "Decorator.h"
#include <iostream>

namespace NS_DECORATOR {

class ConcreteDecoratorB : public Decorator
{
public:
	ConcreteDecoratorB(Component *component) : Decorator(component) {}
	virtual ~ConcreteDecoratorB() {}
	virtual void operation(void)
	{
		Decorator::operation();
		addBehavior();
	}
	void addBehavior(void)
	{
		std::cout << "Move" << std::endl;
	}
};

} /* namespace NS_DECORATOR */

main

#include "Decorator/ConcreteComponent.h"
#include "Decorator/ConcreteDecoratorA.h"
#include "Decorator/ConcreteDecoratorB.h"
using namespace NS_DECORATOR;
using namespace std;
int main(void)
{
	ConcreteComponent cc;
	cc.operation();

	cout << "----------" << endl;

	ConcreteDecoratorA cda(&cc);
	cda.operation();

	cout << "----------" << endl;

	ConcreteDecoratorB cdb(&cda);
	cdb.operation();
}

附加：