Object Oriented Programming (OOP) - CS304 Power Point Slides Lecture 10

8/13/2019 Object Oriented Programming (OOP) - CS304 Power Point Slides Lecture 10

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Object Oriented Programming

(OOP)Lecture No. 10


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Review

Copy constructors

Destructor

Accessor Functions

this Pointer


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this Pointer

There are situations wheredesigner wants to returnreference to current objectfrom a function

In such cases reference is

taken from this pointer like(*this)


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Example

Student Student::setRollNo(int aNo)

{

return *this;}

Student Student::setName(char *aName)

{

return *this;

}


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Example

int main()

{

Student aStudent;

Student bStudent;

bStudent = aStudent.setName(Ahmad);

bStudent = aStudent.setName(Ali).setRollNo(2);

return 0;}


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Separation of interface andimplementation

Public member function exposed by aclass is called interface

Separation of implementation fromthe interface is good softwareengineering


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Complex Number

There are two representations ofcomplex number

Euler formz = x + iy

Phasor form

z = |z| (cos + isin )z is known as the complex modulusand is known as the complex

argument or phase


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Example

float getX()

float getY()void setNumber

(float i, float j)

float xfloat y

Complex

Old implementation

float getX()

float getY()void setNumber

(float i, float j)

float zfloat theta

Complex

Newimplementation


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Example

class Complex{ //oldfloat x;

float y;

public:

void setNumber(float i, float j){

x = i;

y = j;

}

};


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Example

class Complex{ //newfloat z;

float theta;

public:

void setNumber(float i, float j){

theta = arctan(j/i);

}

};


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Advantages

User is only concerned about waysof accessing data (interface)

User has no concern about theinternal representation andimplementation of the class


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Student.h

class Student{

int rollNo;

public:

void setRollNo(int aRollNo);int getRollNo();

};


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Student.cpp

#include student.h

void Student::setRollNo(int aNo){

}

int Student::getRollNo(){

}


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Driver.cpp

#include student.h

int main(){

Student aStudent;}


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There are functions that aremeant to be read only

There must exist a mechanismto detect error if such functions

accidentally change the datamember

constMember Functions


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Keyword constis placed at the

end of the parameter list



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Declaration:

class ClassName{

ReturnVal Function() const;

};

Definition:

ReturnVal ClassName::Function() const{

}


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Example

class Student{

public:

int getRollNo() const{return rollNo;

}

};


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Example

bool Student::isRollNo(int aNo){

/*undetected typing mistake*/

if(rollNo = aNo){return true;

}

return false;}


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Example

bool Student::isRollNo

(int aNo)const{

/*compiler error*/

if(rollNo = aNo){

return true;

}

return false;

}


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constFunctions

Constructors and Destructorscannot be const

Constructor and destructor areused to modify the object to a welldefined state


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Example

class Time{

public:

Time() const {} //error~Time() const {} //error

};


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constFunction

Constant member functioncannot change data member

Constant member functioncannot access non-constant

member functions


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Example

class Student{

char * name;

public:

char *getName();void setName(char * aName);

int ConstFunc() const{

name = getName(); //error

setName(Ahmad);//error}

};


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this Pointer and const MemberFunction

this pointer is passed as constantpointer to const data in case of

constant member functionsconst Student *const this;

instead ofStudent * const this;

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Object Oriented Programming (OOP) - CS304 Power Point Slides Lecture 10