Re: fyi - Mac OS native GDL2 / GSWeb Installer package

[Tim McIntosh]

On Mar 11, 2008, at 2:02 PM, David Ayers wrote:

> Hello Tim.
>
> just a quick status report...
>
> Tim McIntosh schrieb:
>
> > I think I was being too vague with regard to KVC.  I wasn't  
> > referring to
> > the deprecated KVC methods issue that has been discussed on the list
> > recently, but something much more trivial.  All I was talking about  
> > was
> > the difference in behavior of -[NSDictionary valueForKey:] and
> > -[NSDictionary storedValueForKey:] with respect to "special keys"
> > (GDL2's @"allKeys" vs. Cocoa's @"@allKeys"),  and the different  
> > handling
> > of NSArray aggregate functions when there is a key path following the
> > aggregating operator instead of a simple key.
> >
> > For example:   address@hidden@count
> >
> > With Cocoa's -[NSArray valueForKeyPath:] behavior, this would invoke
> > [object valueForKeyPath: @"address@hidden"] on each object in the
> > display group, then return the sum of the counts.
>
> This definitely doesn't work with WO45, but I think it is a natural
> extension of its concepts.  So I'm inclined to attempt to support it.
>
> The funny thing is, that I think we already could do this if  
> NSObject's
> valueForKeyPath: would invoke valueForKeyPath: on the result of the
> valueForKey: of the first component with the remaining key path  
> instead
> of calling valueForKey: with each component.

Seems that way to me, but it sounds like -base is just following the  
Apple documentation, which says:  "The default implementation gets the  
destination object for each relationship using valueForKey: and  
returns the result of a valueForKey: message to the final object."

> Yet this is currently just a theory and I suppose you were having  
> issues
> on Cocoa's Foundation?

From the above, it sounds like Cocoa's NSObject works the same as - 
base, but I didn't test it.

Note: On Cocoa, I think it worked to just eliminate -valueForKeyPath:  
entirely from EOKeyValueCoding.m for this specific example, since  
Cocoa's NSArray implements a fixed set of operators, which includes  
the @sum and @count operators (see http://developer.apple.com/documentation/Cocoa/Conceptual/KeyValueCoding/Concepts/ArrayOperators.html) 
.  However, since Cocoa does not implement the generalized/extensible  
behavior as found in EOF, I figured it would be better to stick with  
the implementation in EOKeyValueCoding if it could be made to provide  
a superset of what Cocoa supports.

> > With GDL2's behavior, this would attempt to invoke [[object  
> > valueForKey:
> > @"itemsArray"] decimalValue] on each object in the display group, sum
> > the results, and then invoke [result valueForKey: @"@count"] on the
> > sum--none of which would actually work as intended in this case.
>
> Actually I'm not sure I get this far yet with -base.  But it's  
> something
> I think we could handle.

I'm not sure how far it was actually making it.  I thought I was  
crashing on the -decimalValue message being sent to an array, but it's  
been too long since I actually debugged it to remember for sure.

> I think this deserves a feature request bug report.  Maybe you could
> open one (assign it to gdl2 and me if that's possible).  Possibly  
> attach
> you patch also.

https://savannah.gnu.org/bugs/index.php?22565

(Didn't see where I could assign you but I added you for e-mail  
notifications.)

-Tim