Re: ObjC data structure for C++/ObjC++ objects?
Re: ObjC data structure for C++/ObjC++ objects?
- Subject: Re: ObjC data structure for C++/ObjC++ objects?
- From: "Jonathan Bailey" <email@hidden>
- Date: Sat, 8 Nov 2008 00:46:44 -0500
Hi Andrew -
Thanks for the suggestion. Sadly, I have to support a large user-base
of people still running 10.4, otherwise I would definitely have gone
for the NSHashMap. :P
Best, JB
On Sat, Nov 8, 2008 at 12:33 AM, Andrew Merenbach
<email@hidden> wrote:
> Greetings, Jonathan,
>
> If you can afford to target 10.5+ only, you can use an NSMapTable, which is
> a mutable type of collection "modeled after NSDictionary" but "can contain
> arbitrary pointers (its contents are not constrained to being objects)"; it
> can also "hold weak references to its keys and/or values." It's probably a
> little more friendly than using CFMutableDictionary. Hope this helps!
>
> Cheers,
> Andrew
>
> On Nov 7, 2008, at 9:12 PM, Jonathan Bailey wrote:
>
>> Hi Michael -
>>
>> Thanks much for your response. I actually did originally intend to use
>> an STL map, but I couldn't get it to work. It seemed that when I added
>> a C++ object to a map declared as an instance variable within my
>> ObjC++ class's header file, this generated an "EXC_BAD_ACCESS" signal
>> - and no exception thrown. As a test, I created a temp STL map in the
>> implementation/.mm file for this class, and added my C++ object to
>> that map and it seemed to work fine. So I assumed that templated
>> classes weren't supported as instance variables for an ObjC++ class.
>>
>> I'll definitely investigate using CFMutableDictionary instead if
>> indeed STL won't work for instance variables.
>>
>> Thanks, JB
>>
>>
>> On Fri, Nov 7, 2008 at 10:29 PM, Michael Ash <email@hidden>
>> wrote:
>>>
>>> On Fri, Nov 7, 2008 at 8:41 PM, Jonathan Bailey <email@hidden>
>>> wrote:
>>>>
>>>> Hi all -
>>>>
>>>> I am trying to find a way to create a dynamically-growable objective C
>>>> data structure within objective C++ code, such as a
>>>> NSMutableDictionary, that can store values that are pointers to an
>>>> objective C++ or straight-up C++ object.
>>>>
>>>> NSMutableDictionary seems to only accept pointers to objective C
>>>> objects, however, and not to arbitrary objects. This seems like a
>>>> simple thing to do but I am a bit stumped. Does anyone know of a way
>>>> to do this?
>>>
>>> CFMutableDictionary will accept arbitrary pointers, and allows you to
>>> provide callbacks so that it knows how to work with them.
>>>
>>> As an added bonus, CFMutableDictionary is "toll-free bridged" to
>>> NSMutableDictionary, meaning that you can simply cast the pointer and
>>> use it. The bridging is not 100% with custom callbacks, as there are
>>> parts of the NSMutableDictionary API which assume that you are storing
>>> only Objective-C objects, but for dictionaries which actually are
>>> storing Objective-C objects it's very useful. This also means that you
>>> can store it in other Cocoa collections like NSArray, other
>>> NSDictionaries, etc.
>>>
>>> And note that if you're using Objective-C++, there's nothing
>>> preventing you from using STL collections for this sort of thing, if
>>> they do what you like.
>>>
>>> Mike
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