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In my iOS app, I'm downloading content from the web into my /Library/Caches directory. I'd like to represent this directory as an NSBundle for better compatibility with some of the external APIs we're using. (That way, we can simply change [[NSBundle mainBundle] pathForResource...] to [myBundle pathForResource...] whenever it appears.)

The following seems to work fine:

NSArray* paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
NSString* cachesDirectory = [paths objectAtIndex:0];
NSBundle* bundle = [NSBundle bundleWithPath:cachesDirectory];

Better yet, the bundle reflects any changes I make to the /Library/Caches directory. However, I'm concerned because the caches directory is technically not a bundle per Apple's docs. That is to say:

  • It's not a "directory with a standardized hierarchical structure that holds executable code and the resources used by that code", since there's no code.
  • It's neither an Application, Framework, nor a Plug-In bundle.
  • It's most like an Application bundle, but it doesn't contain the required Info.plist or executable.

I could find no mention anywhere of this sort of dynamically-created, resource-only bundle. Is this okay to do?

Archagon
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2 Answers2

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Yes, it's absolutely okay to have a resources only bundle. Some of the verbage that you quote pre-exists iOS. In OS X you can dynamically load executable code, that's specifically excluded in iOS.

Localization is an example of resource only bundles.

Edit:

The Bundle Programming Guide says:

Although document formats can leverage the bundle structure to organize their contents, documents are generally not considered bundles in the purest sense. A document that is implemented as a directory and treated as an opaque type is considered to be a document package, regardless of its internal format. For more information about document packages, see “Document Packages.”

which says:

There are several ways to access the contents of a document package. Because a document package is a directory, you can access the document's contents using any appropriate file-system routines. If you use a bundle structure for your document package, you can also use the NSBundle or CFBundleRef routines. Use of a bundle structure is especially appropriate for documents that store multiple localizations.

also note that Apple has been telegraphing that it is minimizing the use of "path"/NSString APIs in favor of URL APIs, though existing path APIs will no doubt continue for many more major OS releases.

bshirley
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  • Is this specifically documented anywhere, though? I'm hesitant to do something like that without Apple's approval, since things might change in the future. – Archagon Sep 21 '11 at 16:59
  • Thank you for the link! I'm not exactly sure what Apple means by using "a bundle structure for your document package", though. It kinda sounds like they want something extra in the directory, but don't specify what. – Archagon Sep 21 '11 at 17:29
  • i think they're hinting at localization – bshirley Sep 21 '11 at 20:26
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The /Library/Caches directory will lack some of the standard files which are required in a bundle, like a Contents/ directory or a Contents/Info.plist file, so it may not behave properly when treated as one. Proceed with caution.