Re: Why can't I use any object as a key in a dictionary?
Re: Why can't I use any object as a key in a dictionary?
- Subject: Re: Why can't I use any object as a key in a dictionary?
- From: Rick Mann <email@hidden>
- Date: Mon, 1 Feb 2010 00:51:18 -0800
Oh I see. Have to use "pure" CFDictionary.
Well, it's all moot, since I can just story the object with the CALayer. Thanks for that!
--
Rick
On Feb 1, 2010, at 00:49:23, Roland King wrote:
> As I said in my earlier mail, if I set up a CFDictionary() which is not copy for keys and retain for values, then I don't use tollfree bridging and use the NSMutableDictionary mutators because they don't work. (in my experience)
>
> I use CFDictionaryAddValue() instead.
>
> When checking for keys or iterating them, I will happily use the tollfree bridged methods however as I've not had the same problem with them.
>
> Rick Mann wrote:
>> On Feb 1, 2010, at 00:40:28, Jean-Daniel Dupas wrote:
>>> Don't bother with custom callback, CFType one works with any objects.
>> Well, that was the one I tried first, but it failed with the same error.
>>> Le 1 févr. 2010 à 09:32, Rick Mann a écrit :
>>>
>>>
>>>> I tried doing this:
>>>>
>>>> const void*
>>>> retainCallback(CFAllocatorRef inAlloc, const void* inValue)
>>>> {
>>>> NSObject* val = (NSObject*) inValue;
>>>> [val retain];
>>>> return val;
>>>> }
>>>> void
>>>> releaseCallback(CFAllocatorRef inAlloc, const void* inValue)
>>>> {
>>>> NSObject* val = (NSObject*) inValue;
>>>> [val release];
>>>> }
>>>>
>>>> CFDictionaryKeyCallBacks
>>>> sKeyCallbacks =
>>>> {
>>>> 0,
>>>> retainCallback,
>>>> releaseCallback,
>>>> NULL,
>>>> NULL,
>>>> NULL
>>>> };
>>>>
>>>> CFDictionaryValueCallBacks
>>>> sValCallbacks =
>>>> {
>>>> 0,
>>>> retainCallback,
>>>> releaseCallback,
>>>> NULL,
>>>> NULL,
>>>> NULL
>>>> };
>>>>
>>>> - (BOOL)
>>>> application: (UIApplication*) inApp
>>>> didFinishLaunchingWithOptions: (NSDictionary*) inOptions
>>>> { mFactoriesByLayer = (NSMutableDictionary*)
>>>> CFDictionaryCreateMutable(kCFAllocatorDefault,
>>>> 3,
>>>> &sKeyCallbacks,
>>>> &sValCallbacks);
>>>>
>>>> .
>>>> .
>>>> .
>>>>
>>>> [mFactoriesByLayer setObject: factory forKey: factory.layer];
>>>>
>>>> }
>>>>
>>>> But the setObject fails.
>>>>
>>>> However, since you say I can store arbitrary keys on the object, that's the better way to go. I didn't realize one could do this.
>>>>
>>>> Thanks!
>>>>
>>>> On Feb 1, 2010, at 00:26:53, Roland King wrote:
>>>>
>>>>
>>>>> Tollfree Bridging is a little more complicated than that. They may end up being the same object under the covers, but even if they are, the NSDictionary version doesn't come with the range of options that the CFDictionary does. Just make a CFDictionary(), the default for it is to retain keys (and values) so it's actually really, really easy; I use them all over the place for stuff like this.
>>>>>
>>>>> If a have a non-NSDictionary compatible CFDictionary() like that by the way I use toll free bridging for reading values from it, but I don't use it for setting them, it doesn't seem to work.
>>>>>
>>>>> By the way, CALayer is a KVC compliant class so you can in fact just store a reference to an arbitrary object in it with
>>>>>
>>>>> [ layer setValue:value forKey:@"KeyForObjectAssociatedWithLayer" ];
>>>>>
>>>>> and save yourself a whole world of pain.
>>>>>
>>>>> Richard Penwell wrote:
>>>>>
>>>>>> I thought NSDictionary and CFDictionary were the same data object, that whole toll free bridging...
>>>>>> An ugly hack would be to cast the pointer to a numeric type, and encode that in a NSNumber... but I would feel very very ashamed of doing so.
>>>>>> On Feb 1, 2010, at 3:10 AM, Roland King wrote:
>>>>>>
>>>>>>> Because NSDictionary requires keys to be copyable because it copies them (it's in the documentation). Use a CFDictionary() instead, you can set it up to retain the keys and do what you want.
>>>>>>>
>>>>>>> Rick Mann wrote:
>>>>>>>
>>>>>>>
>>>>>>>> I'd like to use a CALayer object as a key in a dictionary. The reason is that when my app detects a hit in a layer, I need to quickly determine which object I've associated with it. Since I can't store a reference to an arbitrary object in the CALayer, a dictionary seems to be the most expedient way to do that.
>>>>>>>> Unfortunately, I can't seem to add my layer as the key (it fails with "-[CALayer copyWithZone:]: unrecognized selector sent to instance 0x50132a0"). It's really pretty handy to be able to use any object as a key, why is this not the case in Obj-C?
>>>>>>>> TIA,
>>>>>>>> Rick
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>>>>>>>
>>>>>>> _______________________________________________
>>>>>>>
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>>>> _______________________________________________
>>>>
>>>> Cocoa-dev mailing list (email@hidden)
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>>>
>>> -- Jean-Daniel
>>>
>>>
>>>
>>>
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