Re: Class clusters: MacOSX/GNUstep differences?

[Ronan Collobert]

Hello

> Sure, but there are lots of instances where using some or all of the
> initialisers is helpful for the case of the different storage.  For
> instance, when an array stores in a linked list, or a sparse array of
> some sort.

I agree.

> Sure, new subclasses add new initialisers which call the designated
> initialiser. It's no more of a nonsense to call -initWithObjects:count:
> than to call -init

Yes. The only problem is that in the NextStep and Cocoa frameworks, it is
specified that you have to call -init in class clusters. As I said before,
I didn't find anything concerning OpenStep. (Is there some hidden docs
about OpenStep somewhere??).

> how you want to design your subclass.  The aim of designated
> initialisers is to make as much of the superclass usable by subclasses
> as possible, thus saving effort in many cases ... it's not going to help
> for all cases, but it's never going to be worse than the MacOS-X scheme.

I totally agree. Actually, I'm not sure exactly about the ultimate aim of
GNUstep. I have nothing against adding functionalities. But if it could be
possible to have a complete compatibility (even if it is using
STRICT_MACOS_X compatibility flags at the compilation) with MacOSX, I
think it could be great. After all, I think that a lot of Objective C
developers are coming from MacOSX world.

> > by
> > - (id) initWithObjects: (id*)objects count: (unsigned)count
> > {
> >   return nil;
> > }

> I think that looks quite reasonable ... though you would want the
> default implementation of -initWithObjects:count: to return self rather
> than nil wouldn't you?

Yes. Unfortunately, it seems it does not solve completely the problem: in
Cocoa, the designated initializer in class clusters is -init. Therefore,
if for example I create a subclass of NSMutableArray which implements the
initWithCapacity: method
- (id) initWithCapacity:(unsigned int) n
{
   if( (self = [super init]) )
   {
     // my stuff here
   }
}
It will work in Cocoa (note: I tried to be sure), but in GNUstep it will
create an infinite loop, because the init method of NSMutableArray call
initWithCapacity (the designated initializer in GNUstep).

Ronan.