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?

Quartziferous

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.

Quartziferous

Do you know of an alternative or a workaround to accept a null value, because we're using this on data from a JSON API which has null in some places? – Switchblade

according to this source opensource.apple.com/source/CF/CF-1153.18/CFPropertyList.c (search for CFPropertyListRef CFPropertyListCreateDeepCopy) it's not quite possible. Maybe try replacing null with predefined constant that is unlikely to be encountered in your data set? – Quartziferous