Spring 2008 Mark Fontenot CSE Honors Principles of Computer Science I Note Set 8 1

Quick Look 2 Class Diagrams More 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 person Professor 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 Class Need a CurvedActivity class multiplies the raw score by a curve value before setting the score

GradedActivity.h 6 #ifndef GRADEDACTIVITY_H #define GRADEDACTIVITY_H // Grade class declaration class 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 GradedActivity.h This function will be overridden in the derived class CurvedGrade

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'; else Letter = 'F'; } GradedActivity.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); } CurvedActivity.h Calls the base class member function

CurvedActivity.h 9 void setPercentage (float c) { percentage = c; } float getPercentage() { return percentage; } float getRawScore() { return rawScore; } }; CurvedActivity.h

gradeDriver.cpp 10 // main driver #include #include “CurvedActivity.h” using namespace std; int main() { CurvedActivity exam; float numericScore, percentage; cout > numericScore; cout > percentage; exam.setPercentage (percentage); exam.setScore(numericScore); cout << exam.getRawScore() << exam.getScore() << exam.getLetter(); return 0; } gradeDriver.cpp

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 function objects 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 Binding function call is bound to function implementation at compile time Dynamic 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 functions Declared 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