NSBundle is very useful, and includes an excellent method that returns the path to a file:

- (NSString *)pathForResource😟NSString *)name ofType😟NSString *)extension

This method, however, requires two strings, which didn't work for my app. So I wrote the extension. I realize you could use:

[bundle pathForResource:[string stringByDeletingPathExtension] ofType:[string pathExtension]];

but mine is easier:

[bundle pathForResource:string];

Download extension