设计模式-装饰器

时间：2024-07-08 11:50:45

        装饰器模式是一种结构型设计模式，它允许在运行时扩展一个对象的功能，而不需要改变其现有结构。这种模式的核心思想是通过创建一个装饰器来动态地增强或修改原有对象的行为。装饰器模式是继承的一个补充，提供了比继承更加灵活的方式来扩展对象的行为。

一、编码

  1、头文件

#ifndef _DECORATE_H__
#define  _DECORATE_H__
#include <iostream>
using namespace  std;
/// 抽象被装饰者
// template<class T,class U>  class Decoratee {
//     public:
//         virtual  U  execOpt(T t) = 0 ;
// };

// template<class T,class U> class DecorateImpl: public Decoratee {
//      public:
//          U  execOpt(T t);
// };

/// 抽象被装饰者
class  Decoratee{
   public:
      int  value;
      virtual  void  decorateeOpt() = 0 ;
};

/// 被装饰者的具体实现
class DecorateeImpl : public Decoratee{
    public: 
       DecorateeImpl();
       void  decorateeOpt() override;
};

/// 定义装饰器接口
class  Decorator : public Decoratee {
    protected:
       Decoratee* decoratee;
    public:
       /// @brief  装饰器增强方法
       virtual  void  decoratorOpt() = 0;
};

/// 扩展装饰器A
class  DecoratorImplA : public Decorator {
    public:
        DecoratorImplA(Decoratee* decoratee);
        void  decorateeOpt() override;  
        void  decoratorOpt() override;
};

/// 扩展装饰器B
class  DecoratorImplB : public Decorator {
    public:
        DecoratorImplB(Decoratee* decoratee);
        void  decorateeOpt() override;  
        void  decoratorOpt() override;
};

#endif

 2、函数定义

#include "decorate.h"

// template<class T,class U>
// U  DecorateImpl<T,U>::execOpt(T t) {
//     cout << "" << endl;
// }

DecorateeImpl::DecorateeImpl(){
    this->value = 1;
}

void  DecorateeImpl::decorateeOpt(){
   this->value = this->value + 2; 
   cout << "DecorateeImpl  execOpt  value = " << this->value << endl;
}


DecoratorImplA::DecoratorImplA(Decoratee* decoratee) {
   this->decoratee = decoratee ;
}

void  DecoratorImplA::decorateeOpt(){
    if(this->decoratee== nullptr){
        return;
    }
    this->decoratee->decorateeOpt();
    this->decoratorOpt();
}

void  DecoratorImplA::decoratorOpt(){
    this->decoratee->value =  this->decoratee->value * 5;
    cout << "DecoratorImplA  execOpt  value = " <<  this->decoratee->value << endl;
}


DecoratorImplB::DecoratorImplB(Decoratee* decoratee) {
   this->decoratee = decoratee ;
}

void  DecoratorImplB::decorateeOpt(){
    if(this->decoratee== nullptr){
        return;
    }
    this->decoratee->decorateeOpt();
    DecoratorImplB::decoratorOpt();
}

void  DecoratorImplB::decoratorOpt(){
    this->decoratee->value =  this->decoratee->value * 10;
    cout << "DecoratorImplB  execOpt  value = " <<  this->decoratee->value << endl;
}

二、测试

Decoratee*  decoratee = new DecorateeImpl();
Decorator*  decoratorA = new DecoratorImplA(decoratee);
Decorator*  decoratorB = new DecoratorImplA(decoratee);
decoratorA->decorateeOpt();
decoratorB->decorateeOpt();

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