6. 装饰器

UML

• 聚合(Aggregation)关系：大雁和雁群，上图中空心菱形+箭头表示聚合关系
• 组合(Composition)关系：大雁和翅膀 ，实心菱形+箭头表示组合(Composition)关系

测试代码

#include 
#include 
#include //锁头文件
 
using namespace std;
 
class Component{
public:
    virtual void Operation() = 0;
    virtual ~Component(){
 
    }
};
class ConcreteComponent:public Component
{
public:
    void Operation(){
        cout << "ConcreteComponent" << endl;
    }
};
 
class Decorator:public Component{
protected:
    Component *component = nullptr;
public:
    void SetComponent(Component *_component){
        this->component = _component;
    }
    void Operation(){
        if(component != nullptr){
            component->Operation();
        }
    }
};
class ConcreteDecoratorA:public Decorator
{
private:
    string addedState;
public:
    void Operation(){
        Decorator::Operation();
        addedState = "new State";
        cout << "具体装饰对象A的操作" << endl;
    }
};
 
class ConcreteDecoratorB:public Decorator
{
public:
    void Operation(){
        Decorator::Operation();
        AddedBehavior();
        cout << "具体装饰对象B的操作" << endl;
    }
private:
    void AddedBehavior()
    {
        cout << "AddedBehavior" << endl;
    }
};
int main(void)
{
    ConcreteComponent *c = new ConcreteComponent();
    ConcreteDecoratorA *d1 = new ConcreteDecoratorA();
    ConcreteDecoratorB *d2 = new ConcreteDecoratorB();
    d1->SetComponent(c);
    d2->SetComponent(d1);
    d2->Operation();
    cout << "--endl--" << endl;
    return 0;
}
 

输出

ConcreteComponent
具体装饰对象A的操作
AddedBehavior
具体装饰对象B的操作
--endl--

装饰模式是利用SetComponent来对对象进行包装的。这样每个装饰对象的实现就和如何使用这个对象分离开了，每个装饰对象只关心自己的功能，不需要关心如何被添加到对象链当中

装饰模式变身

如果只有一个ConcreteComponent类而没有抽象的Component类，那么Decorator类可以是ConcreteComponent的一个子类。同样道理，如果只有一个ConcreteDecorator类，那么就没有必要建立一个单独的Decorator类，而可以把Decorator和ConcreteDecorator的责任合并成一个类

根据这段文字的描述，UML结构图变身后的形态

C++改写后的UML图和代码

代码：

#include 
#include 
#include //锁头文件
 
using namespace std;
 
//“Person”类（ConcreteComponent）
class Person{
public:
    Person(){
    }
    Person(string _name):name(_name){
    }
    virtual void Show(){
        cout << "装扮的：" << this->name << endl;
    }
private:
    string name;
};
//服饰类（Decorator）
class Finery:public Person
{
public:
 
    Person *component = nullptr;
    void Decorate(Person *_component){
        this->component = _component;
    }
    virtual void Show(){
        if(component != nullptr){
            component->Show();
        }
    }
};
class fengyi:public Finery
{
public:
    virtual void Show(){
        cout << "风衣" << endl;
        Finery::Show();
    }
};
 
class yundongxie:public Finery
{
public:
    virtual void Show(){
        cout << "运动鞋" << endl;
        Finery::Show();
    }
};
class mojing:public Finery
{
public:
    void Show(){
        cout << "墨镜" << endl;
        Finery::Show();
    }
};
class kouzhao:public Finery
{
public:
    void Show(){
        cout << "口罩" << endl;
        Finery::Show();
    }
};
class xifu:public Finery
{
public:
    void Show(){
        cout << "西服" << endl;
        Finery::Show();
    }
};
int main(void)
{
    cout << "装扮1" << endl;
    Person *p1 = new Person("lkmao");
    fengyi *fy = new fengyi();
    yundongxie *ydx = new yundongxie();
    fy->Decorate(p1);
    ydx->Decorate(fy);
    ydx->Show();
 
    cout << endl << "装扮2" << endl;
    Person *p2 = new Person("laoliu");
    mojing *mj = new mojing();
    kouzhao *kz = new kouzhao();
    xifu *xf = new xifu();
    mj->Decorate(p2);
    kz->Decorate(mj);
    xf->Decorate(kz);
    xf->Show();
 
    cout << "--endl--" << endl;
    return 0;
} 

输出

装扮1
运动鞋
风衣
装扮的：lkmao
 
装扮2
西服
口罩
墨镜
装扮的：laoliu
--endl--

参考：https://blog.csdn.net/yueni_zhao/article/details/128946954