Polymorphism - Object Oriented Programming - Lecture Slides, Slides of Object Oriented Programming

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Object-Oriented Programming

(OOP)

Lecture No. 30

Polymorphism – Case Study

A Simple Payroll Application

OO Model

Employee

SalariedEmp HourlyEmp CommEmp

getName calcSalary

sales commRate

hours hourlyRate

salary

calcSalary calcSalary

calcSalary

name taxRate

String

String operator = operator <<

pStr

Class Employee

class Employee {

private: String name; double taxRate; public: Employee( String&, double ); String getName(); virtual double calcSalary() = 0;

}

Class SalariedEmp

class SalariedEmp : public Employee

{

private:

double salary;

public:

SalariedEmp(String&,double,double); virtual double calcSalary();

}

… Class SalariedEmp

SalariedEmp::SalariedEmp(String& n,

double tr, double sal) : Employee( n, tr ) { salary = sal;

}

double SalariedEmp::calcSalary() {

double tax = salary * taxRate; return salary – tax;

}

… Class HourlyEmp

HourlyEmp ::HourlyEmp( String& n,

double tr, int h, double hr )

: Employee( n, tr ) { hours = h; hourlyRate = hr;

}

… Class HourlyEmp

double HourlyEmp::calcSalary()

{

double grossPay, tax;

grossPay = hours * hourlyRate; tax = grossPay * taxRate;

return grossPay – tax;

}

… Class CommEmp

CommEmp::CommEmp( String& n,

double tr, double s, double cr ) : Employee( n, tr ) {

sales = s; commRate = cr;

}

… Class CommEmp

double CommEmp::calcSalary()

{

double grossPay = sales * commRate;

double tax = grossPay * taxRate;

return grossPay – tax;

}

…A Sample Payroll

void generatePayroll(Employee* emp[], int size) {

cout << “Name\tNet Salary\n\n”;

for (int i = 0; i < size; i++) { cout << emp[i]->getName() << ‘\t’ << emp[i]->calcSalary() << ‘\n’; }

}

Sample Output

Name Net Salary

Aamir 14250

Fakhir 7520

Fuaad 14400

Shape Hierarchy Revisited

Shape

Line Circle Triangle

draw

calcArea

draw

calcArea

draw

calcArea

draw

calcArea

Shape Hierarchy

class Shape {

…

public:

Shape(); virtual void draw(){ cout << “Shape\n”; } virtual int calcArea() { return 0; }

};