observerdesignpatt.cpp

C++ program for Observer Design Pattern

/*
BE Comp H
Title:Observer Design Pattern
*/
#include <iostream.h>
#include<conio.h>
#include<string.h>
static int i;

class Subject {
   int a,b;
public:


   void setVal( int x,int y )
     {
       a=x;
       b=y;
       notify();
     }
   int  getVal_a()
     {
	return a;
     }

    int  getVal_b()
     {
	return b;
     }

   void notify();
};
Subject s;


class Observer
{  protected:
   int x,y;

   public:

   void update(int e,int f)
   {
     x=e;
     y=f;
   }

};





class AddObserver : public Observer
{
public:

  void display()
   {
   cout<<"\nThe Addition is:"<<x+y;
   }

};

class MulObserver : public Observer
{
public:

  void display()
   {
   cout<<"\nThe Multiplication is:"<<x*y;
   }

};

AddObserver ad;
MulObserver ml;

void Subject::notify()
{
 ad.update(s.getVal_a(),s.getVal_b());
 ml.update(s.getVal_a(),s.getVal_b());
}

void main( void )
{
   int a,b;
   char ch;
   clrscr();

   do
   {
   cout<<"\nEnter value for a and b\n";
   cin>>a>>b;
   s.setVal(a,b);

   ad.display();
   ml.display();

   cout<<"\n\nChange a and b? ";
    ch=getche();
   }while(ch=='y'||ch=='Y');



   getch();

}

/*

Enter value for a and b
5
6

The Addition is:11
The Multiplication is:30

Change a and b? y
Enter value for a and b
7
8

The Addition is:15
The Multiplication is:56

Change a and b? y
Enter value for a and b
8
9

The Addition is:17
The Multiplication is:72

Change a and b?
*/