🚀 go-pugleaf

Hi.

I recently posted about a function that would not recognise
a structure and it's variables. Thanks to all who replied,
and I have the problem fixed now. I hope this information
may be of some use. Especially to newbies like me who don't
know about these sorts of facts.

The intention...

Using Borland TC3, I had 3 functions. "Main", "Vpcmenu" and
"Prntitem". "Main" printed a title box then called "vpcmenu"
to display and get input about a main menu. This declared a
structure to hold information about the individual menu
items. I delared an array of 9 structures and a pointer to
them, then initialised them with thier data. In a loop I
passed the value of the pointer to the function "prntitem",
whose job was to print the contents of the pointed-to
structure on the screen in the correct place.

The problem...

I had a compiler error in the function "prntitem" where I
tried to use the variables within the structure. The error
said the variables were undeclared. I was also told that the
pointer I passed was never used. I tried moving the
structure declaration to global and just inside main but no
dice; the function "prntitem" didn't recognise the
structure.

The answer...

It was because I was using seperate source files for each of
the functions. I assumed that because the structure had been
defined 'upwind' of the function that wanted to use it the
compiler would just take the data from each file, make a
program and the scope would be OK . Oh, no! In Borland at
least (I don't know about other compilers) structure
definitions, includes and god only knows what else is only
valid for the source file it is in. Split into multiple
source files and you have to repeat the declarations.

The cure...

Creating a header file with the information in it and
including it in each and every source file. The following is
a better explanation cut from a reply... my thanks to
"tljones1" and all the others who replied.

-----------------------------------------------------------
> files shouldn't matter? The compiler should sort that out shouldn't 
> it? Maybe not...

nope... the compiler won't sort things out for you.  What is
defined in one source file isn't in another.  Believe it or
not, but it keeps you from running into problems.  You have
to explicitly declare your types in each source file you
intend to use them in.  and the best way to do that is to
have a include file that declares that..  For example
mystuff.h would have all of the declarations for the source
file mystuff.cpp (so it has all of the structure
declarations, global variables, function prototypes, etc.)
and mystuff.cpp would include mystuff.h (it is also standard
that mystuff.h has all of the other inncludes that
mystuff.cpp would need).  Also another other source file
that needed to use the types declared in mystuff.h would
also include mystuff.h

I hope this makes sense... take it easy...
-----------------------------------------------------------

If anything I've said is inaccurate, please publicly correct
me. But this has worked for me. Now for the next bit,
getting input and checking for specific keypresses. (Arrows,
numbers and enter)... sigh. I'll get there in the end. With
the help of some friends. Thanks.


---
Mic.
From windy, damp, but clearing skies Worthing; England.
mikebarnard@mistral.co.uk