Share global variables between classes

[daviddoria]

I had a global variable that could be seen by all of my functions. I was getting too many functions in the same file, so I made functions.h and functions.cpp. I put the function definitions in functions.cpp and the declarations in functions.h. In main.cpp, I include functions.h. The problem is, now I can't see the global variables in the functions that I have moved! Is there a way to see them still?

I thought I might just have to move the global variable definition to BEFORE the include statements, but that didn't change anything, I still get "undeclared identifier".

Thanks,

Dave

[BlackJavaBean]

You might be able to get by with using a macro.

//function.h
#define GLOBAL 9000

In this case, any file that includes funtion.h will have access to a macro called GLOBAL, the result will replace every instance of GLOBAL with the value 9000 during preprocessing. If you go this route, be careful because macros don't follow C++ rules exactly.

[daviddoria]

sure I could use a define, but I need to determine the value of this variable at the beginning of the program, so I can't #define it! So can you just not see this type of global variable inside another .cpp file?

[BlackJavaBean]

I getcha, you need to define a global variable that is determined at runtime... Yeah, #define won't do that, unless you want a really ugly macro. Another option is to create a function that creates/passes the global value between files - if you have a lot of globals, it may be a resource hog.
But (this may be Java speaking) if I remember correctly, globals are scoped only to the single source file. So once you leave their file, they go out of scope.

[ivailosp]

http://www.bilmuh.gyte.edu.tr/gokturk/introcpp/icpp_scope.html

[daviddoria]

great link! I haven't tried it yet, but it seems like I have to "re" define the variable using the "extern" command:

void FuncThatCantSeeTheVariable()
{
extern int TheVariable;
cout << TheVariable;
}

I'll report back with results.

Thanks!

Dave