On 2009 Apr 23, at 13:53, Melissa J. Turner wrote:
Unwinding to the original message, the most correct thing to do would be to add a derived property letterGrade which is automatically updated whenever grade is, which then allows you to search against that.
I don't know if a "derived property" is a managed property that appears in the .xcdatamodel, or a regular instance variable.
If Melissa is referring to a managed property, if it is non-transient, then yes this could be used in the predicate of a Core Data fetch. The disadvantage is that now every object in every store has this redundant (derived) attribute. More important than the wasted bits is that custom setters are now required to keep the derived attribute in sync with its source attribute, opening a way to introduce bugs into future versions.
If Melissa is referring to a regular instance variable, then it cannot be used in the predicate of a Core Data fetch and thus filtering must be done in RAM by -[NSArray filteredArrayWithPredicate], resulting in limited scalability.
For my application, I chose the latter. Am I misunderstanding anything? _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
