Quincey, David, Thank you for the detailed explanation.
Regards Sasikumar JP On 11 August 2016 at 12:34, Quincey Morris < quinceymor...@rivergatesoftware.com> wrote: > On Aug 10, 2016, at 23:32 , Sasikumar JP <jps...@gmail.com> wrote: > > > what was the reason NSNumber conforms to NSCopying protocol. > > > 1. It actually inherits conformance from its superclass, NSValue. > > 2. The fact than an object is immutable does not (in general) mean that a > copy can be represented by the same object reference. For example, an > object that contained its own date of creation might be immutable, but a > copy might have a different date, and therefore be a different object. > Putting this another way, the immutability does not make NSCopying > conformance irrelevant. > > 3. NSNumber is one of a group of classes that represent “serializable” > objects (for property lists, for example). Since these are often arranged > in heterogenous hierarchies using arrays, sets and dictionaries, it’s > convenient that they share behavior. If all property list classes conform > to NSCopying, then property lists can be deep copied without special code. > > 4. Objects used as NSDictionary keys must conform to NSCopying. It would > be a hardship if this excluded NSNumber. > > So it turns out to be easier to have NSNumber conform to NSCopying, than > to avoid conformance. > > _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
