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Re: nil in NSArray
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Re: nil in NSArray


  • Subject: Re: nil in NSArray
  • From: Clark Mueller <email@hidden>
  • Date: Sat, 13 Dec 2008 18:39:57 -0800

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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  • Follow-Ups:
    • Re: nil in NSArray
      • From: Mike Schrag <email@hidden>
    • Re: nil in NSArray
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References: 
 >nil in NSArray (From: Mike Schrag <email@hidden>)
 >Re: nil in NSArray (From: Clark Mueller <email@hidden>)
 >Re: nil in NSArray (From: Mike Schrag <email@hidden>)

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