Decorator Design Pattern C++

 

In object-oriented programming, the decorator pattern is a design pattern that allows behavior to be added to an individual object, dynamically, without affecting the behavior of other objects from the same class.

 

 

 

 

 

 

#include<iostream>

using namespace std;

 

class pizza{

                public:

                virtual string getdescription() =0;

                virtual int price() = 0;

};

 

class plainpizaa:public pizza{

                public:

                virtual string getdescription()

                {

                return "plain pizza";       

                }

 

                virtual int price()

                {

                                return 5;

                }

};

 

class pizzaDecorator:public pizza{

protected:

                pizza *m_pPizza;

 

public:

                pizzaDecorator(pizza *_piza):m_pPizza(_piza){}

 

                virtual string getdescription()

                {

                                return m_pPizza->getdescription();;       

                }

 

                virtual int price()

                {

                                return m_pPizza->price();

                }

};

 

class tomato:public pizzaDecorator

{

public:

                tomato(pizza *_pizza)

                                :pizzaDecorator(_pizza){}

 

                string getdescription()

                {

                                string temp = m_pPizza->getdescription();

                                temp +="Tomato";

                                return temp;

                }

                int price()

                {

                                return m_pPizza->price() + 2;     

                }

};

class cheese:public pizzaDecorator

{

public:

                cheese(pizza *_pizza)

                                :pizzaDecorator(_pizza){}

 

                string getdescription()

                {

                                string temp = m_pPizza->getdescription();

                                temp +="cheese";

                                return temp;

                }

                int price()

                {

                                return m_pPizza->price() + 1;     

                }

};

 

int main()

{

 

                pizza *p = new tomato(new cheese(new plainpizaa()));

                cout<<p->price();

               

                return 0;

}

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Command design pattern in C++

Definition By Wiki:

Command pattern. In object-oriented programming, the command pattern is a behavioral design pattern in which an object is used to encapsulate all information needed to perform an action or trigger an event at a later time.

There are 2 examples in the below given code one with the device and other with stock buy,sell order

// cmd pattern decouples the commands and the underlying object

// you just need to pass the underlying concrete object on which you want to call the command

// to the command concrete object

//

#include<iostream>

using namespace std;

//#define TV_EXAMPLE

#define STOCK_ORDER

#ifdef TV_EXAMPLE

class cmd{

public:

virtual void execute()=0;

};

class device{

public:

                virtual void on() = 0;

                virtual void off() = 0;

                //virtual void volincrease() = 0;

                //virtual void voldcrease() = 0;

};

class tv:public device{

public:

                void on()

                {

                cout<<"TV on";

                }

                void off()

                {

                cout<<"TV off";

                }

};

class on:public cmd{

public:

                on(device *_d):d(_d){}

                device *d;

void execute()

{

                d->on();

}

};

class off:public cmd{

public:

                off(device *_d):d(_d){}

                device *d;

void execute()

{

                d->off();

}

};

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C/c++ compilation process detailed

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