Re: Finding and Loading Bundles

[Richard Frith-Macdonald]

On 16 Jun 2009, at 23:49, Stefan Bidigaray wrote:

> I'll try to be to the point... I'm need to be able to find some  
> bundles that conform to a particular protocol so that I can load  
> them and maybe use them.  I've been reading the Apple docs and I  
> already know how to search the bundle directories and use - 
> conformWithProtocol:.  What I'm having a hard time grasping is, how  
> do I find out if the bundle I'm looking at actually meets my  
> criterias before loading it?  Is this even possible?  Since NSBundle  
> doesn't support unloading (at least according to Apple) I don't want  
> to load every single bundle in the system just to then find out they  
> are just going to take up space.  I've read the Apple Plug-in docs  
> and NSBundle Programming Guide, but I still don't know how to do  
> what I'm trying to.

I'm not at all sure you can.

It's true to say that you can't unload bundle code ... the gnu runtime  
doesn't support it, and while I think I read somewhere that Apple's  
new 64bit runtime would support it, the standard one definitely didn't  
last time I looked.

As far as I'm aware, there's no convention for storing the protocols  
supported by a bundle's principal class in its info.plist, so I don't  
see how you can check what a bundle does without loading the code.

I think the normal way that an application determines which bundles to  
load is by using its own directory/filename conventions,  so you just  
search the bundle directories for bundles with the correct names or  
bundles in subdirectories with the correct names.

> FYI: this is for the NSSound reimplementation effort...  I'm trying  
to support multiple "plug-ins".

Well, as NSSound is a gui class, presumably bundles for it should  
count as gui library resources.  In GNUstep we do have a standard  
location for gui library resources, and the GNUstep extension [NSBundle 
+bundleForLibrary:version:] returns the bundle for that location.  The  
problem is, that only returns the bundle in the first domain found  
(assumed to be the one associated with the library being used), and I  
guess with plugins you would want to allow bundles to be provided by  
something other than the standard gui library.

So, I think you are going to have to define your own conventions for  
this.
I would suggest using  
NSSerarchPathForDirectoriesInDomains(NSLibraryDirectory,  
NSAllDomainsMask,YES) to get a list of library directories, then look  
for specific naming patterns in those library directories.
eg.

Assuming your bundles are those with an 'nssound' extension located in  
the 'Bundles' subdirectory ...

{
  NSString      *path;
  NSArray       *paths;
  NSBundle      *bundle;
  NSEnumerator  *enumerator;
  NSMutableArray *all;

  /* Gather up the paths */
  paths = NSSearchPathForDirectoriesInDomains(NSLibraryDirectory,
                                              NSAllDomainsMask, YES);

  enumerator = [paths objectEnumerator];
  all = [NSMutable array arrayWithCapacity: 10];
  while ((path = [enumerator nextObject]) != nil)
    {
      bundle = [self bundleWithPath: path];
      paths = [bundle pathsForResourcesOfType: @"nssound"  
inDirectory: @"Bundles"];
      [all addObjectsFromArray: paths];
    }

  return all;
}