I've just recently learned from my program that "static" or pointer variables do not neccesseraly mean global program wide. I have a single .h file included for main .cpp and another .cpp file. When I changed the variable in main and read it in the other class it was not the same value as I've set it in the main class, even though it was declared static, or as I've tested even if it is a pointer, in the .h file.

Seems like the only way in C++ to have access to a variable you would like to use in another class is to pass it through a function or a constructor as well as using inheritance. As I recall in Java or C# a static variable or a function can be defined in one class and changed from a class while changing it for all the other classes.

It may be breaking the laws of OOP but I was just wondering if it was possible in C++.

Thank you, and have a nice day!!!

global.hpp

extern int counter;

global.cpp

include "global.hpp"

int counter;

other.cpp

include "global.hpp"

// Use counter.......

And, taking the wonderful example of Rod, if you don't feel like including a whole h(pp) file for a variable, you can extern declare said variable in any place that you want it.

i.e.

void BlaBluBli()

{

int a = 2;

extern int counter = a + 7;

}

As long as you ONLY declare it NON EXTERN once, every other external declaration will be solved by the compiler at link time.

But, DON'T! NEVER! Not even once! As an abuser of global variables, especially at work, especially when I need to do things quickly, I can tell you that usually it comes back to byte you (pun intended!). The hassle, when you decide to expand on your work, far outweighs any gains; usually this is a sign that your overall design has a few flaws in it.

Don't do it, EVER, I mean it :p (or if you do, don't let anyone else play with your globals :p )

Ah lol the extern, completely forgot it existed. I'll take your advice, but I like to make a mess also though, makes me look like I've been working : )

Thank you very much!!!

It may be breaking the laws of OOP but I was just wondering if it was possible in C++.

I don't feel like it is breaking the laws of OOP. It depends on what you need. Sometimes it is used as it is the most convienient approach. Please see info about singleton pattern. It is considered an alternative to global variables.

[quote name='Flopid' timestamp='1356749322' post='5015285']
It may be breaking the laws of OOP but I was just wondering if it was possible in C++.
[/quote]

C++ is a multi paradigm language, so it allows you to follow the "laws" of OOP, as well as a lot of other programming styles.

For values that have to be stored globally, using a global variable is a pretty good idea! ;)

I actually am not very found of singletons; they can, as stated before, be easily abused to take a different role than they were designed. And, again, not a fan about "the role that they were designed for". You NEED one instance, I'm gonna trust that you are a big enough boy to instantiate it only once. You cannot? Oh, I have news for you... you're doing something wrong :) <insert rage replies here>

Also, I've met, more than once, naïve singleton implementation that did more wrong than right; for example in the function I wrote I needed to make sure that the said singleton was "destroyed" (the why's of me needing that are a whole different STUPID story, needles to say, I needed to), and simply checking if the "singleton" instance was != NULL would have the "nice" side effect of instantiating it if it was not instantiated before... WHICH WAS STUPID, error inducing and simply nerve wreaking. Me having to check the implementation of something that advertises itself as a singleton and modify it is not my idea of a fun time :)

Usually, through careful architecture design, no singleton would be implemented... ever... nor global variables. But, sure, as with everything else in C++, you want it, you could usually build/use it; but you usually pay the appropriate price for it