[Adium-devl] A thorny design problem

[Evan Schoenberg]

On Nov 10, 2008, at 2:51 PM, David Smith wrote:

> 	In my ongoing project to get contacts in multiple groups working  
> and simplify the implementation of the offline group, I've been  
> attempting to make visibility of a contact depend on where it's  
> being displayed, rather than being inherent to the contact. With  
> visibility now being recalculated on request instead of cached, this  
> is simply a matter of changing the visible property to also take a  
> 'container' argument.
>
> 	However, this introduces a nasty issue: Part of the visibility  
> logic is shared (handling 'always visible', for example) and part  
> isn't (handling 'show offline' differs between the offline group and  
> regular groups for example). If I duplicate the shared logic it  
> violates Don't Repeat Yourself, with all the expected maintenance  
> headaches that brings. If I leave the visibility logic in one place  
> and add special cases for each type of container, that makes it  
> difficult to extend, and violates encapsulation.

What if rather than an object having a visible property at all --  
which no longer makes much sense if one object can be in multiple  
containers and therefore have a visible state in one situation but an  
invisible state in another -- the logic were delegated to the container?

Container subclasses can call super's implementation to get the shared  
logic, then OR this with their own visibility logic.

Something like:
-[NSObject<AIContainingObject> objectIsVisibile:(AIListObject *)object]
?

Cheers,
Evan
-------------- next part --------------
A non-text attachment was scrubbed...
Name: PGP.sig
Type: application/pgp-signature
Size: 194 bytes
Desc: This is a digitally signed message part
URL: <http://adium.im/pipermail/devel_adium.im/attachments/20081110/f914a8fc/attachment.sig>