cocoa - Does Foundation use Core Foundation? -

to me doesn't seem it. of course don't have sources of foundation, in case of gnustep, take example.

they have nsarray code https://github.com/gnustep/libs-base/blob/master/source/nsarray.m

nowhere in source refer cfarray.

https://github.com/gnustep/libs-corebase/blob/master/source/cfarray.c

same goes cf counterparts. why?

gnustep not same apple's foundation. don't know how gnustep implemented, in apple's foundation, ns , cf counterparts closely linked indeed. say, don't have source foundation, there still many ways detect integration between two. 1 easy-to-spot 1 inspect class of many foundation objects:

nsmutablestring *string = @"foo".mutablecopy; nslog(@"%@", nsstringfromclass(string.class)); 

this little program outputs __nscfstring, clue cfstring's implementation indeed being used under hood. specifically, nsstring , cfstring (as nsarray , cfarray, nsdictionary , cfdictionary, , many other foundation , cf types) toll-free bridged—this means internal structures designed same, such can convert 1 other simple typecast, no expensive conversion process. nsarray doesn't use cfarray, is cfarray.

of course, since it's allowed make own private subclasses of classes nsstring, nsarray, et al., means bridging work, cf functions need able handle case looks cf object objective-c subclass, , use objective-c implementation if is. , reason, corefoundation objects, do have of sources to, make many references ns equivalents, such cfarray source linked below, contains references nsarray.

https://opensource.apple.com/source/cf/cf-1153.18/cfarray.c.auto.html