On Oct 18, 2011, at 5:16 PM, Jens Alfke wrote:
>
> On Oct 18, 2011, at 11:59 AM, Keary Suska wrote:
>
>> In your subclass you could use the machinery afforded by
>> automaticallyPreparesContent, or simply set the content on awakeFromNib or
>> whenever it is needed.
>
> Hm. So in other words I would implement the KVC methods in the subclass
> (-countOfEntries, etc.), then implement
> - (void)prepareContent {
> self.content = [self valueForKey: @“entries”];
> }
> to get the fake NSMutableArray and set it as the controller’s content. I
> guess that would work.
Well, "entries" in this case is redundant. If you subclass is designed to
manage an array of "entries", then its content would simply be the array
itself. There is no need to abstract it out by the key. In fact, it is a code
smell to do so.
When dealing with collections even the best of us forget that in the MVC
approach the model for the NSArrayController is the array itself, and not the
object that contains it. The key and the collection KVC methods are simply a
way to acquire the model object from another object that has a relationship to
it. Therefore, in this case, the content of the object controller is the
reference to the model.
It may be useful to mention that there are limitations to how
NSObjectControllers and their subclasses respond to KVO, such that if any
object needs direct access to the array's objects you may want to consider
having the array owned by some other object. In particular,
+keyPathsForValuesEffectingKey, which fails to function for key paths through
NSObjectControllers. This might be the basis of Quincy's flat out "don't do it"
recommendation. But for most simple, bindings-only approaches, the above
approach will work fine.
Best,
Keary Suska
Esoteritech, Inc.
"Demystifying technology for your home or business"
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