Re: Detecting running application

[Richard Frith-Macdonald]

On 11 May 2006, at 09:14, Chris B. Vetter wrote:

> Hi,
>
> I'm looking for a way to detect whether a *bundle* is already loaded.
>
> Point is, I'm working on a bundle that can either be loaded
> automatically by adding it to GSAppKitUserBundles() OR implicitly from
> an application through NSBundle -- but only once. If the bundle
> detects another copy already loaded, it is supposed to quietly "exit."
>
> I remember that back in the old days of GNUstep, when you launched an
> application twice, you got an alert that the application is already
> running. So I figured 'registering' the bundle with gdomap(? I think
> that was how it was done back then) would do the trick. However, I
> just launched SystemPreferences twice and no alert.. Uhm?
>
> Does anyone on the list have an idea how I could solve my problem? The
> easiest would probably be an entry to the user defaults that the
> bundle already loaded. However if the application unexpectedly quits,
> the entry wouldn't be removed. So that's not an option.

I'm not sure what you are after here ... you start by talking about  
bundles and give the impression that you are concerned about handling  
things within a single application, but then talk about registering  
with gdomap, implying that you only want one copy of the bundle  
loaded across all applications.

Assuming that you are only concerned about a single application ...

1. if the issue is to prevent the system trying to re-load dynamic  
libraries it has already loaded within an app ... current SVN code of  
NSBundle should do that anyway.  Alternatively, you could register  
for NSBundleDidLoadNotification and add each loaded bundle to an  
NSMutableSet so that those bundles are never deallocated and  
therefore can't be re-created.

2. if you want to make sure a bundle is never created twice in the  
same app, whether it's a bunlde containing code or not,  the thing to  
do is make sure that bundles are never deallocated (since NSBundle  
already ensures that only one copy of a bundle exists at a time).   
You could do that by overriding the -dealloc method in a category.

If you are concerned about multiple applications you really have a  
problem ... you need to synchronize with bundle creation between apps.
I think that means clever category based overriding of -initWithPath:  
so that you perform the synchronisation before calling the original  
initialiser of the bundle.
I guess your apps could use [NSPortNameServer-registerPort:forName:]  
using the bundle path as the port name, and refuse to initialise the  
bundle if the path is in use as the name of another port.  
Alternatively, you could write your own synchronisation mechanism.