C++ ClassesProgramming in C++

Fall 2008

Dr. David A. Gaitrosdgaitros@admin.fsu.edu

C++ Classes

class Time { public: Time(); void setTime(int, int, int) void print24Hour();

void print12Hour(); private: int hour; int minute; int second; };

C++ Classes

• A “class” is very similar to a “struct” but in many ways extends the capabilities and features. – A “struct” is just the data – A “struct” cannot hide the

implementation• The programmer must have an

intimate knowledge of the structure in order to use it

• The programmer has complete access to the structure

C++ Classes

• A “class” can have both data and member functions incorporated into a single package.

• A “class” can incorporate data and function hiding – The programmer of user need not

have access to all of the data– The programmer or user need not

have access to all member functions

C++ Classes

• Here is how it “usually” works:

Mainprogram.cpp

someclass.h

someclass.cpp

The main program includesthe header file “someclass.h”. This file has prototypes for all of the public member functions and public dataitems, if any. There is no actual executable code in “someclass.h”

“someclass.cpp contains theimplementation of the class. It not only includes all of the information in “someclass.h” but also all of the hidden or private member functions and data. It must “#include” the someclass.h file.

C++ Classes

// MainProgram.cpp#include <iostream.h>#include "someclass.h"

Time TodaysDate;int main(void){ TodaysDate.printStandard(); return 0;}

C++ Classes//someclass.h#ifndef TIME_H#define TIME_H

class Time{public:

Time(); Time(int h, int m, int s); ~Time(); void setTime(int h, int m, int s); void printMilitary(); void printStandard();

private: int hour; int minute; int second;

}; #endif

C++ Classes//Someclass.cpp#include <iostream>using namespace std;#include "someclass.h"

Time::Time(int h, int m, int s){

hour = h; minute =m; second = s;

}Time::Time(){

hour =12; minute = 15; second = 0;

}Time::~Time(){

cout << "Time has stopped";}

C++ Classes// someclass.cpp continuedvoid Time::setTime(int h, int m, int s)

{ hour = h; minute =m; second = s;

}void Time::printMilitary()

{ cout

<<hour<<":"<<minute<<":"<<second;}

void Time::printStandard(){

int tempHour; if(hour>12) tempHour = hour-12; else tempHour = hour; cout

<<tempHour<<":"<<minute<<":"<<second;}

C++ Classes

# Makefile – This is a comment# -g turns on debugging options# -I. allows the current directory to contain system # include files. # -c tells the compiler to compile only, don’t link. # -Wno-deprecated turns off deprecated warning messages. # -o names the output file instead of the default a.out#

CC = g++ND = -Wno-deprecatedCFLAGS = -g -I. -c $(ND)LFLAGS = -g $(ND)

MainProgram: MainProgram.o someclass.o$(CC) $(LFLAGS) -o MainProgram someclass.o MainProgram.o

MainProgram.o: MainProgram.cpp someclass.o$(CC) $(CFLAGS) MainProgram.cpp

someclass.o: someclass.h someclass.cpp$(CC) $(CFLAGS) someclass.cpp