Re: NSMutableDictionary requires NSCopying?

[Matt Rice]

On 2007-03-19 02:43:36 -0800 Richard Frith-Macdonald <address@hidden> 
wrote:

> On 19 Mar 2007, at 10:24, Michael Gardner wrote:
>
> > To use a custom key type with NSMutableDictionary, I defined -hash 
> > and
> > -isEqual: but not -copyWithZone:, since the NSDictionary docs say 
> > that
> > keys are retained rather than copied. But when I try to insert a key
> > of that type, I get an NSInvalidArgumentException saying that my 
> > class
> > does not recognize -copyWithZone:. If I add that method, the 
> > exception
> > goes away and everything works fine. I've tried this on both the
> > latest GNUstep release and on trunk. Are the docs just out-of-date?
>
> Yes, the documentation is just wrong. Dictionary keys do need to be  
> copied.
>
> I've fixed the documentation (at least, all the errors I spotted) in  
> svn 
> trunk to say that keys are copied.

possibly worthwile to explain why things are copied and not retained,
if you add a mutable object to a dictionary and subsequently modify 
the object
in a way which modifies the objects -hash value, it would become 
inconsistent
with the hash value stored in the dictionary.