Issues with 'extern' in Objective-C app.

Question

Hi there,
I am currently developing a Cocoa Document-based application, and have so far created an NSArrayController and linked that it to a class in my application. In my Interface Builder file, I have a main window which appears at launch, and another window that is by default, hidden.
I am overriding the NSArrayContoller's 'add:' method via the MyDocument class that comes by default in the project, and with this overridden method wish to open this second window.
Usually, I would just add the window as an outlet in a class of mine to control. The issue here is, I am unable to add the window as an outlet to the NSArrayController object (this is the first time I have dealt with an NSArrayController), and so have added the window as an outlet to another class, named InfoController.
The aim here, is to allow the MyDocument class to access InfoController's window that I have linked.
I have tried using the following in InfoController.h;
extern IBOutlet NSWindow *authenticate;
I also obviously import the InfoController's header file to the MyDocument's header file;
#import "InfoController.h"
This causes an error where the compiler spits the dummy;
"_authenticate", referenced from:
_authenticate$non_lazy_ptr in MyDocument.o
symbol(s) not found
collect2: Id returned 1 exit status
In case you were wondering where I got this idea from, I followed the instructions in the second option - http://www.cocoadev.com/index.pl?GlobalVariablesInCocoa
I would really appreciate any help here.
Please let me know if I need to clarify anything.
Thanks in advance,
Ricky.

Answer 1

Nothing in that article suggests declaring class instance variables as extern.