On Sep 17, 2009, at 05:44, Doug Knowles wrote:
In a CoreData entity called "Topic", I have a to-many relationship
(to other
Topics) called "children" to implement a hierarchy. In a category on
Topic,
I have implemented a property called "orderedChildren" which returns a
sorted array of the children. In order to ensure that
"orderedChildren" is
recognized as a property of the Topic entity, I have defined
"orderedChildren" as an optional, transient attribute of Topic of
unknown
type (since NSArray or id isn't supported). CoreData generates a
property
declaration for ""orderedChildren" with type UNKNOWN_TYPE, and I have
#defined UNKNOWN_TYPE as "id" in my precompiled header.
It's not at all obvious that following this strategy (creating the
transient attribute) does you any good whatsoever. OTOH, it's not at
all obvious that it does any harm WRT to the problem you're having.
What doesn't work is defining a class method
+keyPathsForValuesAffectingOrderedChildren,
which I'd like to use to cause changes in the "children"
relationship to
trigger change notifications for "orderedChildren".
keyPathsForValuesAffectingOrderedChildren is never called. (Overriding
keyPathsForValuesAffectingValueForKey: from a category is verboten.)
Prima facie, the reason 'keyPathsForValuesAffectingOrderedChildren'
doesn't get called would be that nothing is observing the property.
Maybe that aspect deserves attention ahead of the Core Data side of
it. Have you tried writing some debugging code that (a) installs a KVO
observer on the "orderedChildren" property of a Topic object, and (b)
changes the "children" property, to see whether (c)
"observeValueForKeyPath:..." is invoked for key "orderedChildren"?
Narrowing the problem definition might be the most useful thing you
could do.
Also, sorry if it's a stupid question, but you have checked the
console log for exception messages, haven't you? It often happens,
with KVO-related problems, that an application can appear to run
*almost* correctly after an exception is logged and ignored.
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