设计模式08——装饰模式

 

用例：

//decorator.cpp
//装饰模式：动态地给一个对象添加一些额外的职责

#include "gtest/gtest.h"

class Component
{
public:
    Component() {}
    virtual ~Component() {}

    virtual int Operation() = 0;
};

class ConcreteComponent : public Component
{
public:
    ConcreteComponent() {}
    ~ConcreteComponent() {}

    int Operation()
    {
        return 1;
    }

};

class Decorator : public Component
{
public:
    Decorator() {}
    virtual ~Decorator() {}

    int Operation()
    {
        if (component)
        {
            return component->Operation();
        }

        return -1;
    }

    void SetComponent(Component* comp)
    {
        component = comp;
    }

protected:
    Component* component;
};

class ConcreteDecoratorA : public Decorator
{
public:
    ConcreteDecoratorA() {}
    ~ConcreteDecoratorA() {}
    int Operation()
    {
        int tmp = component->Operation();
        return AddBehavior(tmp);
    }

    int AddBehavior(int x)
    {
        return x+1;
    }
};

class ConcreteDecoratorB : public Decorator
{
public:
    ConcreteDecoratorB() {}
    ~ConcreteDecoratorB() {}
    int Operation()
    {
        return AddBehavior(component->Operation());
    }

    int AddBehavior(int x)
    {
        return x+1;
    }
};

TEST(Decorator,decorator)
{
    ConcreteComponent* c = new ConcreteComponent();
    ConcreteDecoratorA* d1 = new ConcreteDecoratorA();
    ConcreteDecoratorB* d2 = new ConcreteDecoratorB();

    d1->SetComponent(c);
    d2->SetComponent(d1);
    EXPECT_EQ(3,d2->Operation());

    delete c;
    delete d1;
    delete d2;
}