Re: Detecting running application

[Richard Frith-Macdonald]

On 11 May 2006, at 12:06, Chris B. Vetter wrote:

> On 5/11/06, Richard Frith-Macdonald <richard@tiptree.demon.co.uk>  
> wrote:
> [...]
> > Assuming that you are only concerned about a single application ...
>
> No. To ensure it's loaded only once in one single application wouldn't
> be a problem, since I can check NSBundle-allBundles.
>
> > If you are concerned about multiple applications you really have a
> > problem ... you need to synchronize with bundle creation between  
> > apps.
>
> Yes. A bundle can be loaded in (at least) three different ways:
>
> 1) An application can load it during startup using NSBundle- 
> initWithPath:
> 2) GSAppKitUserBundles() can be set to load the bundle within the
> 2a) application's "domain" eg. Gorm = { GSAppKitUserBundles = (
> /path/to/bundle ) }
> 2b) NSGlobalDomain
>
> I simply want to make sure that, regardless of which of these three
> cases is used, the bundle would be initialized only once.

All of them use [NSBundle-initWithPath:] eventually.

> I've just tried to use DO, but apparently this will introduce a racing
> condition if two applications are started within just a few seconds,
> eg. during log in.

Not sure what you mean ... one (and only one) of the applications  
should be able to register with a particular name.  If that's not the  
case, then DO name serving is thoroughly broken ... so I suspect any  
problem is with the logic in your code.  If not, there is a bug we  
need to fix in the nameserver code.

> > I guess your apps could use [NSPortNameServer-registerPort:forName:]
>
> The point is that in case (2) above, the applications wouldn't
> necessarily be mine, so I have to do the check either in the bundle's
> +initialize or -init ...

If the application is not yours, then obviously any solution in which  
you code a category to override -initWithPath: will not work since  
other applications won't contain the category.  In fact I don't think  
there is any possible *general purpose* solution unless it's built  
into the gnustep libraries, and adding such a thing there seems  
perverse because I can't immediately see what use it would be to  
people generally.
That could be my failing ... I still don't see what you actually want  
to achieve and why.
Probably a special case solution is fine ... but I don't know what  
special case we are looking at...

I think I'm clear now that you only want one application to be able  
to load bundles , but is that one application per user, one per host,  
one per lan?
Why is it important that only one application is able to load these  
bundles?

Which bundles are they?  If they are all bundles containing code, and  
you control the bundles, or all of them have a principal class which  
inherits from a class you provide, presumably you could do whatever  
clever stuff you like in that class ... you couldn't stop the bundle  
being loaded, but you could completely change the way the bundle  
behaves in different applications.