Re: KVC

[Helge Hess]

On Jun 6, 2007, at 20:53, Chris Farber wrote:
> There are two parts to KVC: the informal protocol, and the  
> implementation. I made the mistake of thinking you were talking  
> about the implementation for two reasons. In your example, you used  
> takeValue:forKey:; if you had overridden takeValue:forKey:, then it  
> would not be our implementation at fault, and if you had not I  
> could only assume that you were trying to set an ivar or call a  
> method, neither of which can contain unicode. I also had not been  
> thinking about key paths…

Not sure whether its obvious, but we are overriding - 
handleQueryForUnboundKey:, so the default -valueForKey: *is*  
triggered and fails due to the ASCII encoding issue.
I think the easiest thing to do is to change the key retrieval  
encoding to UTF-8. This will work for all ASCII keys as-is and the  
ObjC runtime won't complain about UTF-8 either (it will just not find  
anything).

As mentioned initially we do not even expect the object to return  
anything _in this particular case_, instead we expect it to call - 
handleQueryForUnboundKey:. We notice the missing key and then  
continue searching for it by other means (which will then be able to  
resolve it).

Unfortunately the KVC API has no good -canRetrieveValueKey: API.  
(well, somewhat using NSClassDescription, but this has its own  
particular issues ... ;-)

Thanks,
  Helge
--
Helge Hess
http://www.helgehess.eu/