How can I add persistent data to a Cocoa CoreData file?
How can I add persistent data to a Cocoa CoreData file?
- Subject: How can I add persistent data to a Cocoa CoreData file?
- From: Daniel Wambold <email@hidden>
- Date: Sat, 28 Jul 2007 10:29:14 -0400
This is probably a very simply question but I'm a rank novice....
I have created an application in XCode using CoreData and the
xcdatamodel tool included in XCode. The program works fine, but I've
realized that I need to tag the data file with a version number so I
can add features and not run into problems when the data file is not
up to date with the program. Short of re-creating the data file from
scratch, I'd like to:
(1) Look for the presence of a (?NSString) in the data file on
application launch. (Currently, the file is loaded automatically by
the program, as I have set
- (BOOL)applicationShouldOpenUntitledFile:(NSApplication *)sender
to return TRUE. The NSString would only have to exist once, not for
every record in the file, if that's easier.
(2) Initially, find that there is no such NSString and assume the
version is "oldest." Update the file, then add the NSString to the
persistent store (say, "v1.1").
(3) Subsequently, find the NSString, read the stored version data
(say, "v1.1") and decide if that's current or needs updating.
I just don't know what I need to do to create a variable that's then
automatically included in the data that CoreData saves. I'm
suspicious that it's something along the lines of creating an
NSManagedObject, but I don't actually know what an
NSEntityDescription is, despite having read the docs several times.
If anyone has done something like this and could show me the basic
code, I'd be grateful!
-Dan
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