Re: nil in NSArray
On Dec 13, 2008, at 7:40 PM, Mike Schrag wrote: OK -- So what's the official reason why you aren't allowed to put a nil into an Objective-C NSArray? It seems like a pretty silly restriction to me ... Mike - I asked Steve Naroff for you... On Dec 15, 2008, at 10:00 AM, steve naroff wrote: On Dec 13, 2008, at 7:52 PM, Alex Horovitz wrote: Thoughts? Here's Ali Ozer's perspective... If you allow nils in collections, then you can't tell from calls such as objectForKey: or objectEqualToObject: whether the nil return indicates failure or a hit on nil. So you have to have another sentinel, which is what the lower level APIs (NSHashTable, NSMapTable) do, with the added complexity in API of course. Sounds like the kit folks chose to keep the API simpler (at the cost of not allowing 'nil'). Not super compelling, but a design made a long time ago... snaroff -A Alex ~~ Alex Horovitz Chief Technology Officer The Brookeside Group, Inc. 524 Main Street Acton, MA 01720 (o) 978.266.9876 x225 (c) 978.808.0808 (f) 978.266.1555 ahorov...@brookeside.com www.brookeside.com The Brookeside Group, Inc. - Loyalty MattersTM. ___ Do not post admin requests to the list. They will be ignored. Webobjects-dev mailing list (Webobjects-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/webobjects-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
nil in NSArray
OK -- So what's the official reason why you aren't allowed to put a nil into an Objective-C NSArray? It seems like a pretty silly restriction to me ... ms ___ Do not post admin requests to the list. They will be ignored. Webobjects-dev mailing list (Webobjects-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/webobjects-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: nil in NSArray
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). Clark On 13-Dec-08, at 4:40 PM, Mike Schrag wrote: OK -- So what's the official reason why you aren't allowed to put a nil into an Objective-C NSArray? It seems like a pretty silly restriction to me ... ms ___ Do not post admin requests to the list. They will be ignored. Webobjects-dev mailing list (Webobjects-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/webobjects-dev/cpmueller%40mac.com This email sent to cpmuel...@mac.com ___ Do not post admin requests to the list. They will be ignored. Webobjects-dev mailing list (Webobjects-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/webobjects-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: nil in NSArray
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 ___ Do not post admin requests to the list. They will be ignored. Webobjects-dev mailing list (Webobjects-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/webobjects-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: nil in NSArray
On Dec 13, 2008, at 4:40 PM, Mike Schrag wrote: OK -- So what's the official reason why you aren't allowed to put a nil into an Objective-C NSArray? It seems like a pretty silly restriction to me ... Tradition? That is all that I can think of. Chuck -- Chuck Hill Senior Consultant / VP Development Practical WebObjects - for developers who want to increase their overall knowledge of WebObjects or who are trying to solve specific problems. http://www.global-village.net/products/practical_webobjects ___ Do not post admin requests to the list. They will be ignored. Webobjects-dev mailing list (Webobjects-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/webobjects-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: nil in NSArray
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 ___ Do not post admin requests to the list. They will be ignored. Webobjects-dev mailing list (Webobjects-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/webobjects-dev/cpmueller%40mac.com This email sent to cpmuel...@mac.com ___ Do not post admin requests to the list. They will be ignored. Webobjects-dev mailing list (Webobjects-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/webobjects-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: nil in NSArray
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 ___ Do not post admin requests to the list. They will be ignored. Webobjects-dev mailing list (Webobjects-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/webobjects-dev/cpmueller%40mac.com This email sent to cpmuel...@mac.com ___ Do not post admin requests to the list. They will be ignored. Webobjects-dev mailing list (Webobjects-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/webobjects-dev/cpmueller%40mac.com This email sent to cpmuel...@mac.com ___ Do not post admin requests to the list. They will be ignored. Webobjects-dev mailing list (Webobjects-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/webobjects-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
