Core Data / NSTextView breaks only after save

We have an NSTextView and some data saved about its contents in a core data Managed object context. Everything works great while the managed object context st开发者_如何学Goays in memory. However when we save it, we get very weird fetch request behaviors.

For example, we run a fetch request that asks for all elements with a textLocation less than or equal to 15. The first object in the array we get back has a textLocation of 16.

I know I can't get a definitive answer here, as the code is fairly complex. But does anyone know what this issue smells of?

My thought is that we are somehow not getting the proper MOC synced with the NSTextView after saving? What could change that breaks this?

Thanks.

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For example, we run a fetch request that asks for all elements with a textLocation less than or equal to 15. The first object in the array we get back has a textLocation of 16.

Really, the only way to get that is to (in reverse order of likelihood):

1. Mess up ethe definition of the attribute such that you think your are saving one type of numerical info but that you are actually saving another.
2. You've mangled the predicate so that it actually looks for values of 16 or greater. (You can test predicates against an array of dictionaries whose keys have the same names as you Core Data entities.)
3. It's an error in the conversion between a number and a string for purposes of displaying in the UI or logging.

I would start with (3) myself because it seems more common and until you confirm you don't have a display problem, you can't diagnose the other problems.

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I finally managed to work out what was going on. I was setting textLocation using the setPrimitiveValue... just because I didn't want notifications to fire off. Turns out that's a really bad idea, because Core Data didn't know the value had changed. It still thought the value was 15 instead of 16.

Let this be a lesson: never bypass KVO unless you're INSIDE the managed object and you know what you're doing!