Spring 2008

Mark Fontenotmfonten@engr.smu.edu

CSE 2341 - HonorsPrinciples of Computer Science I

Note Set 81

Quick Look

2

Class DiagramsMore inheritance

Class Diagrams

3

Filled in Diamond: Represents composition

One or more students in a ClassSection

Each student is in 0 or 1 class(es)

Class Diagrams - Inheritance

4

Generalization: Person is a general form of Student and Professor.

Student is personProfessor is person

No real idea of multiplicity in generalization

Overriding Member Functions

5

A member function of a derived class may have the same name and signature of a function in the base class

GradedActivity ClassNeed a CurvedActivity classmultiplies the raw score by a curve

value before setting the score

GradedActivity.h

6

#ifndef GRADEDACTIVITY_H#define GRADEDACTIVITY_H// Grade class declarationclass GradedActivity{ private: char Letter; float Score; void determineGrade();public: void SetScore(float S) { Score = S; determineGrade(); } float GetScore() { return Score; } char GetLetter() { return Letter; }}; #endif

Gra

dedA

ctiv

ity.

h

This function willbe overridden in the

derived classCurvedGrade

GradedActivity.h

7

#include “GradedActivity.h" void GradedActivity::determineGrade(void){

if (Score > 89)Letter = 'A';

else if (Score > 79)Letter = 'B';

else if (Score > 69)Letter = 'C';

else if (Score > 59)Letter = 'D';

elseLetter = 'F';

}

Gra

dedA

ctiv

ity.

cpp

CurvedActivity.h

8

#ifndef CURVEDACTIVITY_H#define CURVEDACTIVITY_H#include “Grade.h”class CurvedActivity: public GradedActivity{ protected: float rawScore; float percentage;public: // overridden in derived class void setScore (float s) {

rawScore = s; // base class setScore method GradedActivity::setScore(

rawScore * percentage); }

Curv

edAc

tivi

ty.h

Calls the base class member function

CurvedActivity.h

9

void setPercentage (float c) { percentage = c; }

float getPercentage() { return percentage; }

float getRawScore() { return rawScore; }

};

Curv

edAc

tivi

ty.h

gradeDriver.cpp

10

// main driver#include <iostream>#include “CurvedActivity.h”using namespace std;int main(){ CurvedActivity exam; float numericScore, percentage; cout << “Enter the student’s raw numeric score: “; cin >> numericScore; cout << “enter the curve percentage for this student:”; cin >> percentage; exam.setPercentage (percentage); exam.setScore(numericScore); cout << exam.getRawScore() << exam.getScore() << exam.getLetter(); return 0; }

grad

eDri

ver.c

pp

Overriding Functions

11

If a derived class overrides a base class member function objects of the base class call the base class version of the

member functionobjects of the derived class call the derived class version of

the member function

Overriding Functions

12

class Base{ public: void ShowMsg() { cout << "This is the Base class.\n"; }};

class Derived : public Base{public: void ShowMsg() { cout << "This is the Derived class.\n"; }};int main(void){ Base B; Derived D; B.ShowMsg(); // ShowMsg of base class called D.ShowMsg(); // ShowMsg of derived class called}

This is the Base class.This is the Derived class.

Polymorphism

13

Polymorphism - the ability to take many forms Occurs when member functions in a class

hierarchy behave differently depending on which object performed the function call

Redefinition of a function does not create polymorphism.

Polymorphism

14

class Base{public: doCalc(){//something;} calc() { doCalc(); }};

class Derived:public Base{public: doCalc() {//something different;}};

int main(){ Derived d; d.calc(); return 0}

Which doCalc()gets called?

Binding Times

15

Static Bindingfunction call is bound to function implementation at compile

timeDynamic Binding

function call is bound to a function implementation at run-time depending on the type of the object responsible for the call

Virtual Function

16

A virtual function is a function that expects to be redefined in a derived class.

Compiler performs dynamic binding on virtual functionsDeclared by placing virtual before the return type in

the base class’s function declaration virtual void myFunction();only placed in prototype or header if defined in class