Answer Posted / subeetha

The observer pattern (a subset of the asynchronous
publish/subscribe pattern) is a software design pattern in
which an object, called the subject, maintains a list of
its dependents, called observers, and notifies observers
automatically of any state changes, usually by calling one
of their methods. It is mainly used to implement
distributed event handling systems.


Sample Program:
#include <iostream>
#include <vector>
using namespace std;

class Subject {
// 1. "independent" functionality
vector < class Observer * > views; // 3. Coupled only
to "interface"
int value;
public:
void attach(Observer *obs) {
views.push_back(obs);
}
void setVal(int val) {
value = val;
notify();
}
int getVal() {
return value;
}
void notify();
};

class Observer {
// 2. "dependent" functionality
Subject *model;
int denom;
public:
Observer(Subject *mod, int div) {
model = mod;
denom = div;
// 4. Observers register themselves with the Subject
model->attach(this);
}
virtual void update() = 0;
protected:
Subject *getSubject() {
return model;
}
int getDivisor() {
return denom;
}
};

void Subject::notify() {
// 5. Publisher broadcasts
for (int i = 0; i < views.size(); i++)
views[i]->update();
}

class DivObserver: public Observer {
public:
DivObserver(Subject *mod, int div): Observer(mod, div){}
void update() {
// 6. "Pull" information of interest
int v = getSubject()->getVal(), d = getDivisor();
cout << v << " div " << d << " is " << v / d
<< '\n';
}
};

class ModObserver: public Observer {
public:
ModObserver(Subject *mod, int div): Observer(mod, div){}
void update() {
int v = getSubject()->getVal(), d = getDivisor();
cout << v << " mod " << d << " is " << v % d
<< '\n';
}
};

int main() {
Subject subj;
DivObserver divObs1(&subj, 4); // 7. Client configures
the number and
DivObserver divObs2(&subj, 3); // type of Observers
ModObserver modObs3(&subj, 3);
subj.setVal(14);
}
14 div 4 is 3
14 div 3 is 4
14 mod 3 is 2

Q1. A. What is unary operator? List out the different operators involved in the unary operator. B. What is an adjust field format flag? Q2. A. Distinguish between a # include and #define. B. Can a list of string be stored within a two dimensional array? Q3. A.Explain how a pointer to function can be declared in C++? B.List the merits and demerits of declaring a nested class in C++? Q4. A. What are the syntactic rules to be avoid ambiguity in multiple inheritence? B. Explain the operation of overloading of an assignment operator. Q5. A. Explain how the virtual base class is different from the conventional base classes of the opps. B. Explain how an exception handler is defined and invoked in a Program. Q6. A. What is a binary file? List the merits and demerits of the binary file usagein C++. B. Write short notes on Text Manipulation Routines. C. Write bites in Turbo c++ Header (“Include”) Files.

2726

---

What is meant by stl in c++?

1085

---

What two types of containers does the stl provide?

940

---

how to making game in c++ ?

2656

---

What are the components of stl?

1052

---

Write a C/C++ program to add a user to MySQL. The user should be permitted to only "INSERT" into the given database.

2590

---

Name the different types of stl containers.

1117

---

how to use C++?

2488

---

What is a list in c++ stl?

1117

---

What does stl mean in slang?

1053

---

please visit this site you'll find my question this is my homework please answer it if you can http://easyscience.org/ib/lofiversion/index.php/t36168.html

2203

---

draw a flowchart that accepts two numbers and checks if the first is divisible by the second.

3321

---

a program using one dimensional array that searches a number if it is found on the list of given input numbers given by the user and locate its exact location in the list.

1896

---

What is stl language?

1086

---

Do you like to Submit Questions in Bulk under Same Category?? Then use our Bulk ListerDo you like to Submit Questions in Bulk under Same Category?? Then use our Bulk Lister

2048

---