On Sep 4, 2008, at 23:20, Oleg Krupnov wrote:
You are right, but what KVC messages I should send to the model in
case of unordered sets, e.g. if I use Core Data?
According to the Core Data docs
(http://developer.apple.com/documentation/Cocoa/Conceptual/CoreData/Articles/cdAccessorMethods.html#/
/apple_ref/doc/uid/TP40002154-SW9),
I should call these dynamic accessors
- (void)addDirectReportsObject:(Employee *)value;
- (void)removeDirectReportsObject:(Employee *)value;
Is this contradicting with the KVC rules? I am confused...
For a Core Data to-many property, which is implemented as a
NSMutableSet, you can use:
[employee mutableSetValueForKey:@"directReports"]
as a KVO-compliant set proxy, and send it any messages you would
normally send to a set, such as addObject: or removeObject: or
removeAllObjects or whatever. (I assume you already know that
something like [employee.directReports addObject: value] is *not* KVO-
compliant. It'll update the relationship, but not trigger
notifications to observers of the "directReports" property.)
The dynamic accessors are KVO-compliant convenience methods you can
use instead. addDirectReportsObject: is functionally equivalent to
[[employee mutableSetValueForKey:@"directReports"] addObject: value],
and removeDirectReportsObject: is functionally equivalent to
[[employee mutableSetValueForKey:@"directReports"] removeObject: value].
Possibly these dynamic accessors are a bit more efficient, or perhaps
they use mutableSetValueForKey:, I don't really know, but it's
generally a good idea to use the features that Core Data gives you, if
you can.
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