Classes. OOP & Class Object Terminology File Management

Transcription

1 Classes OOP & Class Object Terminology File Management

2 Object Oriented Programming OOP industry standard C++ is language of choice

3 Object Oriented Programming With OOP and C++ well organized easy to read to design to modify reuse of code facilitated

4 Object Oriented Programming data and their procedures as a single object Key features Encapsulation Data hiding Inheritance Polymorphism

5 Object Oriented Programming What is radius? User Get radius? Circle Object Radius = 5 Radius is 5.

6 Abstract Data Type ADT = a programmer defined data type whose properties (domain [values] and operations) are specified independently of any particular implementation. It has a how and a what.

7 Classes A class is a programmer-defined data type. It consists of data structure and functions which operate on that data.

8 Example of a Class Declaration class Student { public: void PrintGrade(); void addgrade(double grade); double getgpa(); void chngaddr (char addr[ ]); void chngaddr (char addr [ ], char city [ ]); }; private: double GPA; string address1, address2; int num_of_grades; string fullname;

9 Class Declaration Syntax class Name { // usually capitalized public: public members; // usually functions } ; private: Note private members; // usually variables

10 A Few Terms class class member class object (class instance) client

11 Objects An object is an instance of a class. Similarity: int row; This creates an instance of int called row.

12 Objects If the class is Student, the objects may be the individual student names, the student GPAs, the student courses, etc. Student St1, CSE[100]; St1 is an instance of the class Student. (Alfred E. Newman can be the student s data) CSE100 could be an array of 100 students and would be another instance of Student.

13 Objects Student jane, yoko, elvira, CSE100[100] ; jane.addgrade(93.4); yoko.printgrade(); elvira.getgpa(); CSE100[47].chngAddr( Dakoda #4 ); jane.chngaddr( 123 Gnu, Chili, NY );

14 Class Declarations public: private: double GPA; string address1, address2; int num_of_grades; string fullname; cout << jane.gpa; // Private member cout << elvira. num_of_grades;

15 Class Declarations class Student { public: }; int private: ID; cout << jane.id; cout << elvira.id; cout << CSE100[37].ID;

16 Objects and Members PrintGrade addgrade getgpa chngaddr hall function code function code function code function code GPA address Ayn address2 15 Zola num_of_grades 131 fullname Al Hall p u b l i c p r I v a t e sand PrintGrade addgrade getgpa chngaddr GPA 3.45 function code function code function code function code address1 17 Emil address2 9 Gault num_of_grades 93 fullname Jo Sand

17 What can you do with a class? declare as many objects as you like pass class objects as parameters in a function and return them as function values may be automatic

18 What you cannot do? use most built-in operataions add two objects hall + rand compare for equality hall == rand

19 What you can do? work with individual members of a class hall.gpa + sand.gpa hall.gpa == sand.gpa hall.gpa = sand.gpa hall = sand // member-by-member // assignment

20 What you can do? valid operators member selection. hall.getgpa assignment = jane = elvira ; hall.gpa = sand.gpa //for public members

21 Part of Some Client Code: Student hall; // declaration of an object of type Student Student sand; // declaration of an object of type Student double ingrade; // declaration of an object of type double hall.addgrade(84.3); cout << Enter the grade: ; cin >> ingrade; sand.addgrade(ingrade); sand = hall; // member-by-member assigning sand.printgrade(); // the grade will be 84.3

22 Class Scope declaration function call Student presley; presley.getgpa(); SomeClass someobj; double xyz; someobj.getgpa(); getgpa();

23 Data Hiding public class members data

24 Files specification implementation client

25 Files specification.h client.cpp #include specification.h void main() implementation.cpp #include specification.h

26 Specification File class Name { public : public members; // usually capitalized // usually functions } ; private : private members; // usually variables

27 Sepcification File(s) This is timetype.h class TimeType { public: void Set(int hours, int minutes, int seconds); void Increment(); void write() const; bool Equal(TimeType othertime) bool LessThan(TimeType othertime) private: int hrs, mins, secs; };

28 #include "timetype.h" #include <iostream> using namespace std; Implementation File(s) void TimeType::Set( /* in */ int hours, /* in */ int minutes, /* in */ int seconds ) { /* Precondition: Postcondition: } 0 <= hours <=23 hrs == hours && 0 <= minutes <=59 && mins == minutes && 0 <= seconds <=59 && secs == seconds NOTE: This function MUST be called prior to any of the other member functions */ hrs = hours; mins = minutes; secs = seconds; This is timetype.cpp

29 Example void TimeType::Set(int hour, int minu, int secon) { hrs = hour; mins = minu; secs = secon; } * Class Member Functions Syntax type Class_name::function_name(argument list) { function body }

30 Client File(s) #include timetype.h #include <iostream> using namespace std ; void main(){ TimeType appointment; This is diary.cpp } appointment.set(15, 30, 0); appointment.write(); etc.

31 Preprocessor Directives <filename> filename path\filename

32 Files timetype.h diary.cpp #include timetype.h void main() timetype.cpp #include timetype.h

33 Multifile Program timetype.h diary.cpp timetype.cpp compiler compiler diary.obj timetype.obj linker diary.exe

34 Multifile Program timetype.h diary.cpp timetype.cpp datetype.cpp compiler compiler compiler diary.obj timetype.obj datetype.obj linker diary.exe

35 Managing Projects That Use Classes Place class declaration into an interface header file, classname.h. Place the implementation of the functions of this class into a separate implementation file, classname.cpp. Place the client file(s) in separate.cpp files, each of which should have #include classname.h. All client files and classname.cpp should be inserted as part of the project.