CSE 2341 Object Oriented Programming with C++ Note Set #14

1. CSE 2341Object Oriented Programming with C++Note Set #14

2. More on Polymorphism

3. Base Class Pointers • Pointers to a base class object may be assigned the address of derived class objects • The base class pointer will ignore any overridden functions in the derived class

4. Polymorphism class Base { public: void Show() { cout << "This is from the Base class.\n"; } }; class Derived : public Base { public: void Show() { cout << "This is from the Derived class.\n"; } }; int main() { Base *Bptr; Derived Dobject; Bptr = &Dobject; Bptr->Show(); // which Show function executes? return 0; }

5. Polymorphism class Base { public: virtual void Show() { cout << "This is from the Base class.\n"; } }; class Derived : public Base { public: virtual void Show() { cout << "This is from the Derived class.\n"; } }; int main() { Base *Bptr; Derived Dobject; Bptr = &Dobject; Bptr->Show(); // which Show function executes now? return 0; }

6. Classes Derived from Derived Classes • A base class can also be derived from another class A B C

7. Multiple Inheritance • When one class inherits from more than one base class Class B Class A Class C

8. Multiple Inheritance class Date{ protected: int month, day, year; public: Date(int m, int d, int y) { month = m; day = d; year = y; } int getDay() {return day;} int getYear() {return year;} int getMonth() {return month;} };

9. Multiple Inheritance class Time { protected: int hour, minute; public: Time(int h, int m) { hour = h; minute = m; } int getHour() {return hour;} int getMinute() {return minute;} };

10. Multiple Inheritance class DateTime : public Date, public Time { protected: char DTString[20]; public: DateTime(int, int, int, int, int, int); void GetDateTime(char *Str) { strcpy(Str, DTString); } };

11. Multiple Inheritance DateTime::DateTime(int Dy, int Mon, int Yr, int Hr, int Mt, int Sc) : Date(Dy, Mon, Yr), Time(Hr, Mt, Sc) { char Temp[10]; // Temporary work area for itoa() strcpy(DTString, itoa(GetMonth(), Temp, 10)); strcat(DTString, “/”); strcat(DTString, itoa(GetDay(), Temp, 10)); strcat(DTString, “/”); strcat(DTString, itoa(GetYear(), Temp, 10)); strcat(DTString, “ “); strcpy(DTString, itoa(GetHour(), Temp, 10)); strcat(DTString, “:”); strcat(DTString, itoa(GetMin(), Temp, 10)); strcat(DTString, “:”); strcat(DTString, itoa(GetSec(), Temp, 10)); }

12. Multiple Inheritance #include <iostream> #include “datetime.h” int main() { char Formatted[20]; DateTime PastDay(4, 2, 60, 5, 32, 27); PastDay.GetDateTime(Formatted); cout << Formatted << endl; return 0; }

13. Fini ?