Global variable

I have a simlpe project that has a base class and two inherited
classes.
I want to make a variable that gets initialzed and set one time and is
then accessable from all inherited classes.
I therefore made a global variable list in global.h and a function to
initialize them (pointers) in global.cpp.the master class to set the values. The I call the inherited class to
act on the variables but in the inherited class, the variables are not
initialized.
What am I doing wrong?

MickeyM

re: Global variable

mickey.marshall@litepoint.com wrote:You're not reading the FAQ before posting. See FAQ 5.8. Hint: you've
made a mistake on the line 42 of your code.

V
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re: Global variable

mickey.marshall@litepoint.com wrote:you are not posting the code that doesn't work.

Regards,

Zeppe

re: Global variable

<mickey.marshall@litepoint.comwrote:
Too many words and too little code. You should be able to throw something
together that illustrates your problem in ten or 15 minutes. Post *that*.

re: Global variable

On May 15, 11:35 am, Zeppe
<zeppe@.remove.all.this.long.comment.email.itwrote :Here is the sample code:
Main Code
#include "stdafx.h"
#include "test.h"
#include "testDlg.h"
#include ".\testdlg.h"
#include ".\arithmetic.h"

..
..
..
void CtestDlg::OnBnClickedButton1()
{
// TODO: Add your control notification handler code here
int rv;
InitAB();
CAddTwoNumbers Add2;
//CSubtract Sub2;
Arithmetic *ar1=&Add2;
//Arithmetic *ar2=&Sub2;
//ar= new Arithmetic;
ar1->EnterTwoNumbers(2,4);
//ar2->EnterTwoNumbers(8,4);
rv=Add2.Add ();
//rv=Sub2.Sub2 ();

}

Globals.h
#ifndef MYGLOBALS_H
#define MYGLOBALS_H
static int *a1; //this is the global variable
static int *b1; //this is the global variable
void InitAB();
#endif

globals.cpp
#include ".\globals.h"
void InitAB()
{
a1=new int;
b1=new int;
}

Master class (arithmetic.cpp)
#include "StdAfx.h"
#include ".\arithmetic.h"
//#include ".\globals.h"
//extern int a1,b1;
Arithmetic::Arithmetic(void)
{
}

Arithmetic::~Arithmetic(void)
{
}
void Arithmetic::EnterTwoNumbers(int a, int b)// this works fine
{
*a1=a;
*b1=b;

}
void Arithmetic::GetTwoNumbers(int * a, int * b)
{
if (NULL!=a)
if (NULL!=b)
{
*a=*a1;
*b=*b1;
}
}

inherited class

#include "StdAfx.h"
#include ".\arithmetic.h"
//#include ".\globals.h"
//extern int a1,b1;

CAddTwoNumbers::CAddTwoNumbers(void)
{
}

CAddTwoNumbers::~CAddTwoNumbers(void)
{
}
CAddTwoNumbers::Add(void)// a1 and b1 are both NULL here
{
return(*a1+*b1);
}

re: Global variable

mickey.marshall@litepoint.com wrote:The comments are incorrect. Those are not global variables.
Those are file-scoped variables living outside of any function.
The main thing here is to understand that there is a copy of
each in each tranlsation unit.

Replace the word 'static' with the word 'extern', and you get
closer to the truth. You will still need to _define_ those in
some (only one) translation unit before attempting to use them.
I would put the definitions in the same file where 'InitAB' is.
Replace \ with /.

Add here:

int *a1 = 0;
int *b1 = 0;

(those are the definitions)
V
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re: Global variable

On Tue, 15 May 2007 15:08:08 -0400 in comp.lang.c++, "Victor Bazarov"
<v.Abazarov@comAcast.netwrote,More confusing still, according to Mickey's original description they
were supposed to have belonged to the base class, or in c++ terms they
should be static member variables. But a different "static".

And of course there is _nothing_ in the posted code that remotely
justifies making them pointers or using new, which is a very bad thing
to do without a reason. I can only assume that in the real application
there is some reason for it.