Le 13 mars 2013 à 18:13, John McCall <rjmcc...@apple.com> a écrit :
> On Mar 13, 2013, at 2:13 AM, Jean-Daniel Dupas <devli...@shadowlab.org> wrote: >> Le 13 mars 2013 à 01:55, Wim Lewis <w...@omnigroup.com> a écrit : >>> On 12 Mar 2013, at 2:08 AM, Graham Cox wrote: >>>> in a + method, [self class] === self. Once you've got that, you've got it. >>>> >>>> >>>> >>>> You're overthinking this. >>>> >>>> A class method is just an instance method of the class object. No magic at >>>> all. So all this confusion you've caused yourself about [super class] and >>>> so on is wholly unnecessary to correctly use class methods. >>> >>> To be very slightly pedantic, the only magic here is 'super' --- sending a >>> message to super (which you can only do from a method implementation) is >>> special syntax that searches for the method starting with the >>> implementation's class's superclass, rather than at the receiver's actual >>> class. Everything else is non-magic. (In general, that's been one of the >>> strengths of ObjC: very little magic.) >>> >> >> To be ever more pedantic, there is other magic involved when sending a >> message to a class. >> If there is no class method that matches the selector, the runtime will then >> search for instance methods of the root class. > > Note that this isn't "magic" really; it's a quirk of the type system (both > formal and dynamic). The root metaclass is a subclass of the root class. Yes, nothing is magic if the magician reveals its tricks, that's why he should not do that ;-) > This can be problematic if you really want your root class to have a layout > that's bigger than just an isa field, because the ABI and runtime just > hardcode the layout of classes and there is no room for extra fields there — > thus you need to be sure that anything using your extra fields is never > invoked on a class object. I usually avoid this kind of issue by not writing root class. The extra fields issue is not the only one that a root class can have. Even methods that do not access ivars should take care of the Class case (retain/release/autorelease for instance). -- Jean-Daniel _______________________________________________ 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
