Re: NSNull and @""
Re: NSNull and @""
- Subject: Re: NSNull and @""
- From: "Stelian Iancu" <email@hidden>
- Date: Sat, 11 Oct 2008 13:51:55 +0200
On Sat, Oct 11, 2008 at 2:58 AM, Seth Willits <email@hidden> wrote:
> On Oct 10, 2008, at 5:40 PM, Ian Joyner wrote:
>
> I'm just trying to work out what NSNull really is in the Cocoa context. Is
>> it an object in Cocoa?
>>
>
>
> As I said, yes. It's truly an object. (A singleton, as well.)
>
>
>
> Since NSNull may be a "valid" value of any other type, is it counted as a
>> subtype of every other type (hence the ultimate subclass)? I think a good
>> and simple (one that doesn't make my brain hurt) definition of NSNull is
>> important in order to ensure software correctness.
>>
>
> Woah. Talk about brain hurt. You're thinking about this far too much.
>
> There's no inheritance, there's no nothing. It's an object. It's absolutely
> in no way different than you creating your own IJNull class, and sticking an
> instance of it anywhere. It doesn't behave any differently.
>
>
> As for use, the documentation says it pretty clearly:
>
> "The NSNull class defines a singleton object used to represent null values
> in collection objects (which don't allow nil values)."
>
>
> You can't stick nil into dictionaries and arrays. So either you stick an
> empty string, an NSNumber with 0, etc if those are OK, or you can use
> NSNull.
>
>
Hmm, that's weird. In some official iPhone examples from Apple, they do
exactly that: they put nil as the last element in an array. So what's up
with that?
S.
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