C++ 2

Creating Classes and Object

Objectives In this lesson, you will learn to: • Creating Classes • Define member variables • Define member function • Define object • Initialize object

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Creating Classes and Object

Problem Statement You are suppose to develop a module that accepts the student details. the details are given below. Student

student_name [25] mobile_no[11] date_of_birth[9] stud_adress[40]

get() print()

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Creating Classes and Object

Class • A class defines a template for declaring run-time object. • All data within a class excepted to be private. • the public interface to a class consists of function know as methods. • Classes are the user defined datatypes. • The class keyword is used to declare a class.

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Creating Classes and Object Rules for Naming classes in C++ • A class name must not have embedded space or symbol like ? - + ! @ # % ^ & * ( ) [ ] { } . , ; : “ ‘ / and \. But we can use a underscore. • A class must begin with a letter hich may be followed by a sequence of letters or digits (0-9)but the first character of class name cannot be a digit. Class Naming Convention in C++ • A class name should be meaningful • A class should ideally be a noun. •First letter of every world should capital. Like:- EmployeeDetails

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Creating Classes and Object

Access Specifiers • Access specifiers are used to determine whether any other class or function can access the members of class or not. • C++ class support three access specifiers. – public – private – protected

• public access specifiers will expose its members to other function and object.

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Creating Classes and Object

• private access specifiers will hide its members to other function and object. It’s the default access specifiers. • Protected access specifiers will work like private access specifiers and the difference we will study with Inheritance.

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Creating Classes and Object

A simple class class StudentDetails { //class members will come here }; • Here class is a keyword • StudentDetails is a user defined class name

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Creating Classes and Object Now we can write our class class StudentDetails { private: char studName[ 25]; char mobileNo[11]; char dateOfBirth[9]; char studAdderss[40]; public:

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Creating Classes and Object void get() { cout<<“Enter your name “; cin>>studName; cout<<“Enter your mobile no.”; cin>>mobileNo; cout<<“Enter your Date of birth”; cin>>dateOfBirth; cout<<“Enter your Address”; cin>>studAdderss; }

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Creating Classes and Object

void print() { cout<<“Name :”<<studName; cout<<“Mobile no :”<<mobileNo; cout<<“Date of birth :”<
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Creating Classes and Object

• Encapsulation and classes – Object characteristics assembled at one place – Rigid enforcement of access specification.

• Data Abstraction and classes – Hides implementation details – A user-defined data type

Objects • Class cant work on its own so we have to make a working unit of it and the working unit of class is knows as object. • We can also call a object is the instance of class in memory.

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Creating Classes and Object More on objects …….. Polygon class

Polygon objects

Properties: Vertices Border color Abstract Fill color into

Methods: Draw Erase Move

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Creating Classes and Object More on objects ……..

• An object in C++ is an item declared to be a class type Example: StudentDetails sobj; here sobj is the object of StudentDetails class.

• An object is an instance of class. • We can access the member of a object with the . (dot) operator. Now we can write the main for our class as given

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Creating Classes and Object

int main() { StudentDetails sobj; sobj.get(); //calling get function of object sobj.print();//calling print function } After compilation it will accept student it will print the student details.

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Creating Classes and Object

• In the above program if you will call only print function it will print some undesired values because the variables are not being given any initial value. • We can do it with the help of a function knows as constructor. • constructor is a special method automatically invoked when an object of a class is created. • A constructor is called to – Allocate space for the object – Initialize data members

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Creating Classes and Object

More on Constructor….. • Each class can has one or more constructor • A constructor – Can be overloaded – Is a member function with the same name as class – Can have parameter but no return value – Implicitly returns a ‘this’ pointer to created object – It has many types (we will discus then with other topic).

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Creating Classes and Object More on Constructor….. • In our class we will make constructor as class StudentDetails { private: //declare variables as above public: StudentDetails () { // Initialize data members } //create other methods }//close class

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Creating Classes and Object

• The constructor does not take any parameter is knows as default constructor • In case no constructor declared for the class the compiler creates a default constructor in such case ,instantiation of an object of this class invokes the default constructor. A Destructor • Is a member function • Is automatically called when an object is destroyed

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Creating Classes and Object

More on Destructor……. • Has the same name as the class plus a leading tilde (~). • Takes no arguments. • Has no return type • Cannot be overloaded • Usually frees up dynamic memory allocated by object • In our case it will be made like

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Creating Classes and Object More on Destructor……. • In our class we will make constructor as class StudentDetails { private: //declare variables as above public: ~ StudentDetails () { // Initialize data members } //create other methods and constructor }//close class

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Creating Classes and Object We can also write member function out side class by using scope resolution operator(::). class StudentDetails { private: char studName[ 25]; char mobileNo[11]; char dateOfBirth[9]; char studAdderss[40]; public: void get(); void print(); }; //class closed

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Creating Classes and Object

void StudentDetails::get() { cout<<“Enter your name “; cin>>studName; cout<<“Enter your mobile no.”; cin>>mobileNo; cout<<“Enter your Date of birth”; cin>>dateOfBirth; cout<<“Enter your Address”; cin>>studAdderss; }

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Creating Classes and Object void StudentDetails::print() { cout<<“Name :”<<studName; cout<<“Mobile no :”<<mobileNo; cout<<“Date of birth :”<
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Creating Classes and Object

• Write a program to accept the customer details. Class diagram is given below. Customer

custId[4] custName[20] mobileNo[11] dateOfSales[9] custAdress[40] accept() display()

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