On May 14, 2010, at 10:25 AM, Quincey Morris wrote:
If I understand you correctly, you're on the right track -- you want to bind the array controller's selection indexes to your data model's selection property. However, Core Data properties don't support index sets as a standard data type, so you have more work to do. Since NSIndexSet supports NSCoding, your easiest choice is probably to make your selection a transformable attribute. That means Core Data automatically converts the value to and from an archive using a standard transformer.
I see what you are saying. The path I was following was a little different. Each model object has a 'selected' attribute or property. When the array controller selection is set, the model objects 'selected' property is also set. What I was trying to do was figure out how to get each model object's 'selected' property back into the array controller's selection.
You are suggesting that I just use the array controller's selection, which is an index set, and just put that into Core Data. That would work for a transient property but not for an on disk persistent store. The index set of the array controller is based on an in-memory arrangement of model objects and could change and does change from one document opening to the next. But if I do not need persistence this might be the way to go.
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