NetNews Usenet Archive 1992 #16/NN_1992_16.iso/spool/comp/sys/next/programm/5366

Text File | 1992-07-30 | 2.7 KB | 56 lines

Newsgroups: comp.sys.next.programmer
Path: sparky!uunet!nwnexus!sounds!brianw
From: [e-mail] (Brian Willoughby)
Subject: Re: Question about visibility of interface variables
Message-ID: <[e-mail]>
Sender: [e-mail] (Brian Willoughby)
Reply-To: [e-mail]
Organization: SoundSoftware, Bellevue, WA, USA
References: <[e-mail]>
Date: Thu, 30 Jul 1992 07:37:26 GMT
Lines: 43

Darcy Brockbank writes
| In article <[e-mail]> [e-mail] writes:
| > I need to have a couple of variables which are specific to the particular
| > nib section that is loaded.  (I have several of the same nib files on
| > screen at the same time, but each must have its own, discrete data set).  I
| > figure that by putting these variables in the @interface section of the
| > header file, they will be specific, like I need.  However, a large part of
| > my file consists of regular C functions (which run faster, I think, than
| > methods).  When I put the variables in the @interface section, my functions
| > can no longer see them.  I can see what is going on here, and where my
| > problem is.  Does anyone know of a better way of handling this than
| > changing my functions into methods?  Thanks.
| > Kevin
|
| Variables declared in the interface section are global only to that object's
| methods, and the subclasses of that object.

Actually, @interface variables are not global in the K&R sense.  They are local
variables whose scope includes the object and its subclasses.  Just like a
recursively called function will have multiple copies of the same variables,
multiple objects each have their own copy of the @interface variables - they
are not global.

| In order to make private variables that are also available to
| an object's functions you can make static declarations within the
|  .m file. You wan't have access to those variables from subclasses
| though.

Warning: static variables are global and not created for each instance of the
object.  The original question indicated a need for each nib section that is
loaded to have its own discrete data set - static declarations will not provide
discrete instance variables.

To answer the original question, about the only way to have discrete instance
variables accessable by regular C functions would be to allocate a structure
every time you load the nib section and pass the pointer to this structure to
the regular C functions whenever you want to operate on a particular instance
of the nib.  Basically you would have to rewrite the Objective-C runtime - so
why not use it?
--
Brian Willoughby    Software Design Engineer, BSEE
[e-mail]    SoundSoftware
NeXTmail welcome