【初学设计模式】Decorator (装饰)

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类图：













代码实现：



类声明：

/********************************************************************
	File: 		decorator.h	
	Author:		blackboy  blackboycpp@gmail.com
	Purpose:	装饰模式
	Created:	2011-03-16
	Modified:	2011-03-16   19:48
*********************************************************************/

#ifndef  __DECORATOR_H__
#define  __DECORATOR_H__

namespace blackboycpp
{
    //////////////////////////////////////////////////////////////////////////
    class  Component
    {
    public:
        virtual  void  Operation() = 0;
    };

    class  ConcreteComponent : public Component
    {
    public:
        virtual  void  Operation();
    };

    //////////////////////////////////////////////////////////////////////////
    class  Decorator : public Component
    {
    public:
        Decorator();
        Decorator(Component*);
        virtual  void  Operation();
    private:
        Component*  _component;
    };

    class  ConcreteDecoratorA : public Decorator
    {
    public:
        ConcreteDecoratorA();
        ConcreteDecoratorA(Component*);
        void  Operation();
    private:
        void  AddedState();
    };

    class  ConcreteDecoratorB : public Decorator
    {
    public:
        ConcreteDecoratorB();
        ConcreteDecoratorB(Component*);
        void  Operation();
    private:
        void  AddedBehavior();
    };

}

#endif

类实现：

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

namespace blackboycpp
{
    //////////////////////////////////////////////////////////////////////////
    void  ConcreteComponent::Operation()
    {
        std::cout << "ConcreteComponent::Operation()/n";
    }

    //////////////////////////////////////////////////////////////////////////
    Decorator::Decorator()
    {
        std::cout << "Decorator::Decorator()/n";
        _component = 0;
    }

    Decorator::Decorator(Component* p)
    {       
        std::cout << "Decorator::Decorator(Component*)/n";
        _component = p;
    }

    void  Decorator::Operation()
    {
        std::cout << "Decorator::Operation()/n";
        _component->Operation();
    }

    //////////////////////////////////////////////////////////////////////////
    ConcreteDecoratorA::ConcreteDecoratorA() : Decorator()
    {
        std::cout << "ConcreteDecoratorA::ConcreteDecoratorA()/n";
    }

    ConcreteDecoratorA::ConcreteDecoratorA(Component* p) : Decorator(p)
    {
        std::cout << "ConcreteDecoratorA::ConcreteDecoratorA(Component*)/n";
    }

    void  ConcreteDecoratorA::Operation()
    {
        std::cout << "ConcreteDecoratorA::Operation()/n";
        Decorator::Operation();
        AddedState();
    }

    void  ConcreteDecoratorA::AddedState()
    {
        std::cout << "ConcreteDecoratorA::AddedState()/n";
    }
    
    //////////////////////////////////////////////////////////////////////////
    ConcreteDecoratorB::ConcreteDecoratorB() : Decorator()
    {
        std::cout << "ConcreteDecoratorB::ConcreteDecoratorB()/n";
    }

    ConcreteDecoratorB::ConcreteDecoratorB(Component* p) : Decorator(p)
    {
        std::cout << "ConcreteDecoratorB::ConcreteDecoratorB(Component*)/n";
    }

    void  ConcreteDecoratorB::Operation()
    {
        std::cout << "ConcreteDecoratorB::Operation()/n";
        Decorator::Operation();
        AddedBehavior();
    }

    void  ConcreteDecoratorB::AddedBehavior()
    {
        std::cout << "ConcreteDecoratorB::AddedBehavior()/n";
    }
}

main()：

#include <cstdlib>
#include "decorator.h"
using namespace blackboycpp;

int main(int argc, char** argv)
{
    Component*  component = new ConcreteComponent;
    ConcreteDecoratorA*  decoratorA = new ConcreteDecoratorA(component);
    ConcreteDecoratorB*  decoratorB = new ConcreteDecoratorB(decoratorA);
    decoratorB->Operation();
        
    delete decoratorB;
    delete decoratorA;
    delete component;

    system("pause");
    return 0;
}