Re: RFC: [GDL2/base] unableToSetNullForKey: / unableToSetNilForKey:

[David Ayers]

Richard Frith-Macdonald wrote:

> On Monday, March 24, 2003, at 12:12 pm, David Ayers wrote:
>
> > How can we invoke unableToSetNullForKey: on OS X if 
> > unableToSetNilForKey: of NSObject is invoked?
>
>
> You could create a class (called NilToNull for instance) which 
> implements unableToSetNilForKey: by calling unableToSetNullForKey:, 
> and use a call to
> GSObjCAddClassBehavior([NSObject class], [NilToNul class]) to add that 
> method to NSObject.
>
> Of course, you would have to be careful to make this call *after* 
> loading any bundles which might contain categories containing the method.

Thanks Richard,

It took me a while to figure out why it wasn't working... and then to 
realize that this is tough to solve...

void
GSObjCAddMethods (Class class, struct objc_method_list *methods)
{
...
/* As long as the method isn't defined in the CLASS,
put the BEHAVIOR method in there. Thus, behavior
methods override the superclasses' methods. */
...
This is to insure that the behavior mechanism doesn't override 
explicitly implemented methods and this makes sense for most uses of 
behavior. Should/could we implement something like 
GSObjCReplaceMethod(Class class, struct objc_method *old, struct 
objc_method *new) or should this be handled differently?

And even if we can get it to work, I'm not so worried about other 
bundles with the category (for me there is base/Foundation and EOControl 
of GDL2. Anyone else trying to override this, has to worry about the 
ambiguities themselves.) but I'm more worried about actually having the 
initialzation code called in time before any KVC attempts are made. As I 
can't call the function in +load and these are categories on NSObject 
(i.e. I can't use +initialize on NSObject, and it wouldn't help adding 
it to all EOControl classes either, as they needn't be used before KVC 
is used :-(.

This is really tricky.

Cheers,
Dave