Object Oriented Object Oriented ProgrammingProgramming

(OOP)(OOP)Lecture No. 8Lecture No. 8

ReviewReview

►ClassClass ConceptConcept DefinitionDefinition

►Data membersData members►Member FunctionsMember Functions►Access specifierAccess specifier

Member FunctionsMember Functions

►Member functions are the functions Member functions are the functions that operate on the data encapsulated that operate on the data encapsulated in the classin the class

►Public member functions are the Public member functions are the interface to the classinterface to the class

Member Functions (contd.)Member Functions (contd.)

►Define member function inside the Define member function inside the class definitionclass definition

OROR►Define member function outside the Define member function outside the

class definitionclass definition But they must be declared inside class But they must be declared inside class

definitiondefinition

Function Inside Class BodyFunction Inside Class Body

class class ClassName ClassName {{……public:public:ReturnType ReturnType FunctionNameFunctionName() {() {

……}}

};};

ExampleExample►Define a class of student Define a class of student

that has a roll number. that has a roll number. This class should have a This class should have a function that can be used function that can be used to set the roll numberto set the roll number

ExampleExample

class Student{class Student{

int rollNo;int rollNo;

public:public:

void setRollNo(int aRollNo){void setRollNo(int aRollNo){

rollNo = aRollNo;rollNo = aRollNo;

}}

};};

Function Outside Class BodyFunction Outside Class Body

class class ClassNameClassName{{……public:public:ReturnTypeReturnType FunctionName FunctionName();();

};};ReturnTypeReturnType ClassName ClassName::::FunctionNameFunctionName()(){{……

}}Scope

resolution operator

ExampleExample

class Student{class Student{……int rollNo;int rollNo;

public:public:void setRollNo(int aRollNo);void setRollNo(int aRollNo);

};};void Student::setRollNo(int aRollNo){void Student::setRollNo(int aRollNo){……rollNo = aRollNo;rollNo = aRollNo;

}}

Inline FunctionsInline Functions

► Instead of calling an inline function Instead of calling an inline function compiler replaces the code at the compiler replaces the code at the function call pointfunction call point

►Keyword ‘inline’ is used to request Keyword ‘inline’ is used to request compiler to make a function inlinecompiler to make a function inline

► It is a request and not a commandIt is a request and not a command

ExampleExample

inline int Area(int len, int hi)inline int Area(int len, int hi){{return len * hi;return len * hi;

}}int main()int main(){{cout << Area(10,20);cout << Area(10,20);

}}

Inline FunctionsInline Functions

► If we define the function inside the If we define the function inside the class body then the function is by class body then the function is by default an inline functiondefault an inline function

► In case function is defined outside the In case function is defined outside the class body then we must use the class body then we must use the keyword ‘inline’ to make a function keyword ‘inline’ to make a function inlineinline

ExampleExample

class Student{class Student{int rollNo;int rollNo;

public:public:void setRollNo(int aRollNo){void setRollNo(int aRollNo){

……rollNo = aRollNo;rollNo = aRollNo;

}}};};

ExampleExample

class Student{class Student{

……

public:public:

inline void setRollNo(int aRollNo);inline void setRollNo(int aRollNo);

};};

void Student::setRollNo(int aRollNo){void Student::setRollNo(int aRollNo){

……

rollNo = aRollNo;rollNo = aRollNo;

}}

ExampleExample

class Student{class Student{……public:public:void setRollNo(int aRollNo);void setRollNo(int aRollNo);

};};inline void Student::setRollNo(int inline void Student::setRollNo(int

aRollNo){aRollNo){……rollNo = aRollNo;rollNo = aRollNo;

}}

ExampleExample

class Student{class Student{……public:public:inline void setRollNo(int aRollNo);inline void setRollNo(int aRollNo);

};};inline void Student::setRollNo(int inline void Student::setRollNo(int

aRollNo){aRollNo){……rollNo = aRollNo;rollNo = aRollNo;

}}

ConstructorConstructor

ConstructorConstructor

►Constructor is used to initialize the Constructor is used to initialize the objects of a classobjects of a class

►Constructor is used to ensure that Constructor is used to ensure that object is in well defined state at the object is in well defined state at the time of creationtime of creation

►Constructor is automatically called Constructor is automatically called when the object is createdwhen the object is created

►Constructor are not usually called Constructor are not usually called explicitlyexplicitly

Constructor (contd.)Constructor (contd.)

►Constructor is a special function Constructor is a special function having same name as the class namehaving same name as the class name

►Constructor does not have return typeConstructor does not have return type►Constructors are commonly public Constructors are commonly public

membersmembers

ExampleExample

class Student{class Student{……

public:public:Student(){Student(){

rollNo = 0;rollNo = 0;……

}}};};

ExampleExample

int main()int main()

{{

Student aStudent;Student aStudent;

/*constructor is implicitly /*constructor is implicitly called at this point*/called at this point*/

}}

Default ConstructorDefault Constructor

►Constructor without any argument is Constructor without any argument is called default constructorcalled default constructor

► If we do not define a default If we do not define a default constructor the compiler will generate constructor the compiler will generate a default constructora default constructor

►This compiler generated default This compiler generated default constructor initialize the data constructor initialize the data members to their default valuesmembers to their default values

ExampleExample

class Studentclass Student{{int rollNo;int rollNo;char *name;char *name;float GPA;float GPA;

public:public:…… //no constructors//no constructors

};};

ExampleExample

Compiler generated default Compiler generated default constructorconstructor

{{

rollNo = 0;rollNo = 0;

GPA = 0.0;GPA = 0.0;

name = NULL;name = NULL;

}}

Constructor OverloadingConstructor Overloading

►Constructors can have parametersConstructors can have parameters►These parameters are used to initialize These parameters are used to initialize

the data members with user supplied the data members with user supplied datadata

ExampleExample

class Student{class Student{……public:public:Student();Student();Student(char * aName);Student(char * aName);Student(char * aName, int aRollNo);Student(char * aName, int aRollNo);Student(int aRollNo, int aRollNo, Student(int aRollNo, int aRollNo, float aGPA);float aGPA);

};};

ExampleExample

Student::Student(Student::Student(int aRollNo, int aRollNo,

char * aName){char * aName){if(aRollNo < 0){if(aRollNo < 0){

rollNo = 0;rollNo = 0;} } else {else {rollNo = aRollNo;rollNo = aRollNo;}}……

}}

ExampleExample

int main()int main()

{{

Student student1;Student student1;

Student student2(“Name”);Student student2(“Name”);

Student student3(”Name”, 1);Student student3(”Name”, 1);

Student student4(”Name”,1,4.0);Student student4(”Name”,1,4.0);

}}

Constructor OverloadingConstructor Overloading

►Use default parameter value to reduce Use default parameter value to reduce the writing effortthe writing effort

ExampleExample

Student::Student(Student::Student( char * aName = NULL, char * aName = NULL, int aRollNo= 0, int aRollNo= 0, float aGPA = 0.0){float aGPA = 0.0){

……}}Is equivalent toIs equivalent toStudent();Student();Student(char * aName);Student(char * aName);Student(char * aName, int aRollNo);Student(char * aName, int aRollNo);Student(char * Name, int aRollNo, float Student(char * Name, int aRollNo, float aGPA);aGPA);

Copy ConstructorCopy Constructor

►Copy constructor are used when:Copy constructor are used when: Initializing an object at the time of Initializing an object at the time of

creationcreation When an object is passed by value to a When an object is passed by value to a

functionfunction

ExampleExample

void func1(Student student){void func1(Student student){……}}int main(){int main(){Student studentA;Student studentA;Student studentB = studentA;Student studentB = studentA;func1(studentA);func1(studentA);

}}

Copy Constructor (Syntax)Copy Constructor (Syntax)

Student::Student(Student::Student(const Student &obj){const Student &obj){

rollNo = obj.rollNo;rollNo = obj.rollNo;name = obj.name;name = obj.name;GPA = obj.GPA;GPA = obj.GPA;

}}

Shallow CopyShallow Copy

►When we initialize one object with When we initialize one object with another then the compiler copies state another then the compiler copies state of one object to the otherof one object to the other

►This kind of copying is called shallow This kind of copying is called shallow copyingcopying

ExampleExample

Student studentA;Student studentB = studentA;

Name

GPARollNo

studentA

Name

GPARollNo

studentBAHMAD…

Memory

Copy Constructor (contd.)Copy Constructor (contd.)

Student::Student( Student::Student( const Student &const Student & obj){obj){

int len = strlen(obj.name);int len = strlen(obj.name);name = new char[len+1]name = new char[len+1]strcpy(name, obj.name);strcpy(name, obj.name);……//copy rest of the data members//copy rest of the data members

}}

Copy Constructor (contd.)Copy Constructor (contd.)

►Copy constructor is normally used to Copy constructor is normally used to perform deep copyperform deep copy

► If we do not make a copy constructor If we do not make a copy constructor then the compiler performs shallow then the compiler performs shallow copycopy

ExampleExample

Name

GPARollNo

A

Name

GPARollNo

B

AHMAD

Memory

AHMAD

Student studentA;Student studentB = studentA;