Re: Help with NSPointerArray and NSMapTable

On Sep 24, 2009, at 16:24, Adam R. Maxwell wrote:

>
> On Sep 24, 2009, at 2:11 AM, Christiaan Hofman wrote:
>
>>
>> On Sep 24, 2009, at 4:27, Adam R. Maxwell wrote:
>>
>>>
>>> On Sep 21, 2009, at 12:14 PM, Christiaan Hofman wrote:
>>>
>>>> Apart from this, the 64-bit docs warn against type-casting an  
>>>> NSInteger as a pointer, but that seems to be exactly what  
>>>> NSPointerArray expects me to do? If they go against their own  
>>>> docs I really think they should be more clear.
>>>
>>> Can you point to where the docs warn against this?
>>>
>>> thanks,
>>> Adam
>>
>> Right in the Overview of the NSMapTable documentation:
>>
>> "It can contain arbitrary pointers (its contents are not  
>> constrained to being objects).
>
> Oops!  I should have been more specific: where do the docs warn  
> against casting NSInteger to a pointer?  I thought that would be  
> pointer-size on 32 or 64 bit (vs int or long).
>

It's somewhere in the 64-bit transition docs, <http://developer.apple.com/mac/library/documentation/Darwin/Conceptual/64bitPorting/MakingCode64-BitClean/MakingCode64-BitClean.html 
 >.

>> "Note that only the options listed in “NSMapTableOptions” guarantee  
>> that the rest of the API will work correctly—including copying,  
>> archiving, and fast enumeration. If you use other  
>> NSPointerFunctions options, the map table may not work correctly,  
>> or may not even be initialized correctly."
>
> Nice.  That's the same caveat that an Apple engineer pointed out to  
> me for CFDictionary (as an excuse for -[NSMutableDictionary  
> setObject:forKey:] incompatibility with pointer equality  
> callbacks).  Based on that, I'd avoid the NSMapTable class and  
> either use CFDictionary or the NSMapTable C API.

And what are the appropriate callbacks to use for pointers to some  
kind of struct or float? I tried NSOwnerPointerMapValueCallBacks, but  
that did not work. I also don't see how the value callbacks can copy  
the struct or float, because it returns void. Isn't that possible?

Christiaan