Default Instance of entity in Core Data Document
Default Instance of entity in Core Data Document
- Subject: Default Instance of entity in Core Data Document
- From: Frank Schmitt <email@hidden>
- Date: Tue, 31 Jul 2007 10:26:51 -0700
I'm writing a Core Data Document-based application that needs to have
a single instance of one or two settings saved with every document.
The way I'd like to do this is to add an entity (say "MySettings") to
the data model managed by an NSObjectController, whose attributes are
the various settings I need to save. I would then bind a series of UI
elements to the object controller, and the values entered into the UI
would automagically make their way into the file.
I've run into two snags along the way:
First, I need to check for an instance of the entity once my
managedObjectContext is finished loading, and add one if it's
missing. Where is the right place to do this? awakeFromNib seems to
be too early (the objects aren't loaded yet), and I can't do the
usual trick of adding an observer to the object controller's
"content" key, since it won't ever fire if the file contains no
instances of the entity.
The second snag is that modifying the file after it's created always
brings up a "Save Changes?" sheet. I imagine I could reset this with
updateChangeCount, but that seems hackish. Is that in fact the right
way to do this?
Ideally I could change the "blank slate" state of the managed object
context to include one instance of the entity with the default values
that I've assigned in the data model editor. Is there a way to do that?
Thanks,
-Frank
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