Re: Is +[NSMutableArray initialize] completely implemented?

[Kazunobu Kuriyama]

Though this seems to be a dated document, gcc/objc/README of GCC's 
source tells

<quote>
+initialize
===========

This method, if defined, is called before any other instance or class 
methods of
that particular class.  This method is not inherited, and is thus not 
called as
initializer for a subclass that doesn't define it itself.  Thus, each 
+initialize
method is called once (or never if no methods of that particular class 
is never
called).
Besides this, it is allowed ot have several +initialize methods, one for 
each
category.  The order in which these (multiple methods) are called is not 
well
defined.  I am not completely certain what the semantics of this methods is
for other implementations, but this is how it works for GNU Objective C.
<unquote>

Is there anyone who knows further?  Is there a formal document of GNU's ObjC
runtime?

Cheers,
- Kazunobu Kuriyama



David Ayers wrote:

> Richard Frith-Macdonald wrote:
>
> > On 22 Feb 2004, at 11:56, Philip Mötteli wrote:
> >
> > > > > > and that [NSMutableArray+initialize] is called before any other 
> > > > > > method of the class, so I don't know how -initWithCapacity: could 
> > > > > > be called without NSMutableArrayClass being initialised.
> > > > > > or step through in debug yourself to find out what is going on?
> > > > >
> > > > >
> > > > >
> > > > > I set a breakpoint in both +initialize, in NSMutableArray and 
> > > > > NSArray and NSArray's initialize is clearly not called.
> > > >
> > > >
> > > >
> > > > Then I guess for some reason the runtime does not think that 
> > > > NSMutableArray inherits from NSArray ... why not?
> > >
> > >
> > >
> > > I found the problem: I have a +initialize method in a category of 
> > > NSArray. So the runtime system called only this one.
> >
> >
> >
> > Interesting ... it's worth trying to remember that problem because 
> > it's not at all obvious.
> >
> > Perhaps we should have some coding hints somewhere to say things like 
> > ... 'don't override +initilize in a category'
>
> This sounds reasonable... I also fell into that trap before because I 
> believed to have read that +initialize would be called for every 
> category.  But I had confused that with +load which /does/ get called 
> per category.
>
> > Actually, it's not clear to me whether the runtime should try to 
> > detect this situation and call the class implementation before 
> > calling the category implementation ... probably not , as I think 
> > that categories are generally supposed to be responsible for handling 
> > things like that.  Also, what if two or more categories override 
> > +initialize etc.  As far as I know there is no standard way to 
> > resolve the situation where multiple categories override a method.
>
>
> The +load mechanism works because the runtimes invokes it directly 
> (i.e. via implementation pointer when loading the category and not via 
> message lookup.)  I don't think we should try doing the same for the 
> current runtimes wrt +initialize.  Now whether a future unified 
> runtime had similar mechanism that invokes a standardized method per 
> Class/Category after all runtime initialization has been done, is a 
> different issue.
>
> > Perhaps GNUstep should establish some conventions for this and 
> > perhaps provide a few runtime helper functions to assist in managing 
> > this sort of thing.
> > On the other hand, it's rarely an issue ...
>
>
> That's something I think is worth pondering about.
>
> Cheers,
> David
>
>
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