Re: KVC

[Helge Hess]

On Jun 6, 2007, at 24:14, Chris Farber wrote:
> > produces an exception because the ß can't be converted to ASCII. I  
> > recommend switching the conversion to UTF-8.
> I don't believe this is an issue, as you cannot use unicode for  
> variables or method names.

I'm talking about KVC, not methods and ivars. Key-Value Coding is  
defined in terms of

  - (id)valueForKey:(NSString *)_key
  - (void)setValue:(id)_value forKey:(NSString *)_key;

Given your argumentation I could not use @ or - in keys just because  
they are not allowed in vars/method-names.

No restrictions apply to the key. KVC is not just another way to  
access methods, its a concept on its own and in fact there are plenty  
of places where those methods are mapped to something which has  
nothing to do with methods. Eg one of the more complicated ones is  
D2WContext which maps keys to a rule system in Direct2Web.

> > Please remember that KVC is not just for accessing methods but for  
> > arbitary key/value combinations.
> Perhaps you are thinking of NSMutableDictionary?

This is one of the simplest objects which modify the way KVC works.  
EOGenericRecord is another one and a good example where unicode plays  
a role (Given that eg PostgreSQL table, column names can be arbitary  
strings).

> KVC is only for setting properties via appropriately named methods  
> or direct access to instance variables.

Sorry??? Have you ever used WebObjects or EOF (or a clone of  
those)? :-) The power of KVC is that its separate. Eg it allows you  
to do trampolines like this:

  @implementation MyComponent
  - (id)labels {
    return self->labelHandler;
  }
  @end

  @implementation MyLabelHandler
  - (id)valueForKey:(NSString *)_key {
    return [[NSBundle bundle] labelForKey:_key];
  }
  @end

  LocalizableString.strings:
  WelcomeTitle = "Hello Friendly Visitor!!!";

And then in the WO template:
  <#WOString var:value="labels.WelcomeTitle" />



Anyways, to make a long story short: if you want to be compatible  
with Cocoa, you need to allow arbitary keys. This should hopefully  
stop further argumentation ;-)

Thanks,
  Helge

PS: its just a matter of time until UTF-8 is allowed in selectors.  
Java already does this (which BTW also affects KVC in combination  
with Java bridges ...)
--
Helge Hess
http://www.helgehess.eu/