1. Classes Static Members
Department of Computer and Information Science, School of Science, IUPUI
CSCI 240
Classes Static Members
Dale Roberts, Lecturer
Computer Science, IUPUI

2. Static Members Data and Functions Can be static
Exists Independently of Any Instantiated Objects

3. Static Data Members COMMON to All the Objects of that Class
Exist Even When NO Class Objects Exist
Definition for static Data Members is a Declaration in header file
Initialization ONLY by an Initializer or an Assignment Statement inside a static member function
Accessing -- class_name::data_name or object_name.data_name

4. Static Data Members -- Example
// student.h #define size 20 class student{ char *name, *ss; static char *instructor; public: student(char *, char *); ~student(); };

5. Static Data Members – Example (cont)
// student.cpp #include “student.h” #include <iostream> student::student(char *ip_name, char *ip_ss){ name = new char[size]; ss = new char[size]; strcpy(name, ip_name); strcpy(ss, ip_ss);} void student::print(){ cout << "Name: " << name << endl; cout << "SS: " << ss << endl; cout << "Instructor: " << instructor << endl;} }; /* Definition and Initialization of Static member */ char *student::instructor = "Henry";

6. Static Data Members -- Example
// client.cpp #include “student.h” main() { student s1("John", " "); student s2("Tom", " "); s1.print(); s2.print(); }
Name: John SS: Instructor: Henry Name: Tom SS: Instructor: Henry  

7. Static Member Functions
COMMON to All Objects of the Class
Created by the Class Definition -- Exist Even when NO Class Objects Exist
Can Only Access Static Data Members of the Class or other static member functions
Accessing -- class_name::function_name() or object_name.function_name()

8. Static Member Functions -- Example
// student.h #define size 20 class student{ char *name; char *ss; static char *instructor; public: student(char *ip_name, char *ip_ss); static void print_instructor(); };

9. Static Member Functions – Example (cont)
// student.cpp #include “student.h” #include <iostream> student::student(char *ip_name, char *ip_ss){ name = new char[size]; ss = new char[size]; strcpy(name, ip_name); strcpy(ss, ip_ss);} static void student::print_instructor() { cout << "Instructor: " << instructor << endl;} /* Definition and Initialization of Static member */ char *student::instructor = "Henry";

10. Static Member Functions – Example (cont)
// client.cpp #include “student.h” main() { student::print_instructor(); }
Output will be: Instructor: Henry
Notice that no instance of student is required.

11. Acknowledgements
These slides were originally prepared by Rajeev Raje, modified by Dale Roberts.