Difference between CFMutableArray and NSMutableArray?-Collection of common programming errors

OSX’s APIs are layered, there are basic low-level APIs that are self-cotnained and then there are richer APIs built on top of them, in turn using the lower level APIs themselves.

CFMutableArray is part of the CoreFoundation framework and used by the lower-level APIs. NSMutableArray (I guess NS stands for NextStep) is part of the Foundation framework and used in higher level APIs like the AppKit or Cocoa.

Which you should use depends on where you are working. If you’re working in a rich user interface using Cocoa, NSMutableArray is the right choice. If you’re working on a daemon, driver or anything else just using CoreFoundation, use CFMutableArray.

Luckily, as pointed out above, many of these CF/NS types are toll-free bridged and so you can use CoreFoundation APIs from e.g. Cocoa without having to constantly convert types.