And yeah... I guess that example is specific to NSDictionary. In
NSArray's case... something to do with NSKeyValueCoding conformance
maybe?
Clark
On 13-Dec-08, at 6:39 PM, Clark Mueller wrote:
Oh, I see. You wanted explanation. :-)
I suppose that if nothing else it would be for historical reasons,
but I was under the impression there was a point to NSNull.
Specifically, aren't there scenarios where you might want to
distinguish a null pointer from querying for the "presence" of a
null value?
For example, in WO, if you're using an NSDictionary "bindings" for
query bindings, you might want to query for some attribute
"myAttribute" that equals NULL in your database, so you would do
something like bindings.setObjectForKey(NSKeyValueCoding.NullValue,
"myAttribute"). So when EOF is constructing the qualifier, it knows
that it should produce "WHERE my_attribute = NULL", but that when
bindings.objectForKey("myOtherAttribute") is null (as in a null
pointer), it knows that's not an attribute you want to qualify on.
Am I wrong? Wouldn't the same apply to some scenarios in Cocoa in
the context of Core Data? Or certainly, to the defunct Objective-C
version of WO?
Clark
On 13-Dec-08, at 5:58 PM, Mike Schrag wrote:
Cocoa Foundation has NSNull as JavaFoundation does, why not use
that?
The NSNull class defines a singleton object used to represent
null values in collection objects (which don’t allow nil values).
... because it's a lame hack :) ? I know there are workarounds,
but in 2008, I don't expect junk like that. I can't imagine it's
really a null-terminated array in NSArray's implementation. They
almost certainly track count as an int separately, and therefore
wouldn't need null-termination of the internal array.
ms
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