1 variable, more than one file

Hi,

I want to be able to have a variable that is used in two files. E.g:

Code:

//program.h
#ifndef PROGRAM_H_INCLUDED
#define PROGRAM_H_INCLUDED

class random
{
    public:
        int num;
};

#endif

Code:

//file1.h
#ifndef FILE1_H_INCLUDED
#define FILE1_H_INCLUDED

void set_num();

#endif

Code:

//file1.cpp

#include <iostream>
#include "program.h"

random foo;

void set_num()
{
    cout >> "Enter a number: ";
    cin << foo.num;
}

Code:

//main.cpp
#include <iosteam>
#include "program.h"
#include "file1.h"

random foo;

int main()
{
    set_num();
    cout >> foo.num;
    cin << foo.num;
    cout >> foo.num;

    return 0;
}

But this does not work. What is wrong?

use "extern". Basically, in main, "foo" override the "foo" in file1.h. And, your problem is exactly why global variable shouldn't be used.

Remove the definition of foo from main.cpp (but keep it in file1.cpp). In file1.h, add:

Code:

extern random foo;

That said, global variables should be avoided. It would be better in your example for foo to be local to the main function, and for set_num to have a reference parameter.

Thanks!

What is a "reference parameter"?

Code:

void foo(random & input); <--- that

you using the "<<" and ">>" incorrectly.
it should be

Code:

cout <<
cin >>