Recommended way to save NSPredicates in Core Data store?

[Ken Thomases]

I'm building an interface that contains an NSPredicateEditor (think iTunes smart playlists), and I want to save the predicate in a Core Data store. What is the recommended way to do this? Serialize the NSPredicate object and save it as a blob? Break apart the predicate into one or more NSExpressions (left hand value, operator, right hand value) and reconstruct the predicate? I can think of several possibilities, but am wondering what is the path of least resistance (and, I suppose, most binding-friendly!).

Serializing the predicate (using NSKeyedArchiver) seems obviously the right way to go. Any other approach is just reinventing serializing it in a worse way.

You can create a custom value transformer (subclass of NSValueTransformer) to automatically archive and unarchive. Use that on your binding.

Regards,
Ken

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