Using an auto incremented NSNumber as attribute in a NSManagedObject
Using an auto incremented NSNumber as attribute in a NSManagedObject
- Subject: Using an auto incremented NSNumber as attribute in a NSManagedObject
- From: Joshua Preston <email@hidden>
- Date: Thu, 6 Mar 2008 16:05:04 -0500
Hey guys,
First, let me say that I'm just starting to pick up Cocoa and
Objective-C, and so far, I love it. Core Data seems to be an elegant
solution to some of my past problems (mainly Java persistence). I am
however having problems finding information regarding auto incremented
attributes, namely an NSNumber attribute. I've created the attribute
with the Data Modeler and set up all of the relationships I require.
Everything worked, so I read about implementing a subclass of
NSManagedObject and defining a -awakeFromInsert method. This appears
to be working for some of the other fields, such as the date, but I'm
having problems determining how exactly to increment the number.
For example, when I create my first object, I want the numeric id
field to be 1. Each subsequent insert should be the previous numeric
id field + 1. I've read some of the posts regarding performing this
and the general thought on this process is to create an additional
entity in my data model containing the "current maximum index" then
perform fetch, increment and get value of that field and use that for
the incremented value of my new object. I'm not sure if this is still
the only way or even the preferred way to perform this feat. I'm kind
of worried about locking that "counter" field until the new managed
object has been created to avoid any increment problems.
Additionally, I've tried accessing the docs located at the link below,
but I keep getting connection errors, anyone else having problems
accessing the documentation?
http://developer.apple.com/documentation/Cocoa/Reference/CoreDataFramework/Classes/NSManagedObject_Class/Reference/NSManagedObject.html
Regards,
Joshua Preston
email@hidden
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