CFPropertyListCreateDeepCopy fails to process array / dictionary containing NSNull

Question

For some reason this sample code works:

NSArray *immutable = @[ @"a", @"b", @"c" ];
NSMutableArray *mutable = (__bridge  id)CFPropertyListCreateDeepCopy(kCFAllocatorDefault, (__bridge  CFArrayRef)immutable, kCFPropertyListMutableContainers);

and this code produces nil as a result of the conversion:

NSArray *immutable = @[ @"a", [NSNull null], @"c" ];
NSMutableArray *mutable = (__bridge  id)CFPropertyListCreateDeepCopy(kCFAllocatorDefault, (__bridge  CFArrayRef)immutable, kCFPropertyListMutableContainers);

I tried to find any mention of NSNull not being allowed when using this function. I have a suspicion that it has something to do with the way method examines whether property is mutable or not, but I can't really back that up with facts.

Any ideas?

Answer 1

As kind people from apple developer forum pointed out the issue is that Property List Structure is rather strict about data types it can work with. NSNull is not one of allowed ones.

From apple docs:

Property lists are constructed from the basic Core Foundation types CFString, CFNumber, CFBoolean, CFDate, and CFData.