Re: ObjC data structure for C++/ObjC++ objects?

[Andrew Merenbach]

Greetings, Jonathan,




Cheers,
        Andrew

On Nov 7, 2008, at 9:12 PM, Jonathan Bailey wrote:

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!

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 PROTECTED]> wrote:

On Fri, Nov 7, 2008 at 8:41 PM, Jonathan Bailey <[EMAIL PROTECTED]> wrote:

Hi all -


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?

I am trying to find a way to create a dynamically-growable objective C

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

only Objective-C objects, but for dictionaries which actually are

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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parts of the NSMutableDictionary API which assume that you are storing storing Objective-C objects it's very useful. This also means that you

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