On Jun 15, 2009, at 06:43, Sebastian Celis wrote:
I believe I found my issue. In my SCBook class I was overriding didChangeValueForKey:withSetMutation:usingObjects: so that I could store an NSString containing a comma-separated list of tags associated with the book. Apparently this is a very bad way to do it. I missed the big warning in the documentation which states that this method should not be overridden. What is the correct way to do this from inside of the SCBook class?
If the comma-separated list is just for display in the user interface, you could generate it on the fly. Use 'keyPathsForValuesAffectingTagList' (or whatever) to ensure that the proper KVO notifications get sent when the underlying bookTag objects change.
If you really want to store the comma-separated list, you can write your own set accessor overrides (addTagsObject, removeTagsObject, addTags, removeTags) and rebuild the string in the accessors. The only trick here (apart from following the documented pattern for writing the accessors) is to realize that the accessors are also called at undo time, so accessors with a side effect of updating a different property can be problematical unless you're careful.
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