Re: Using an auto incremented NSNumber as attribute in a NSManagedObject

FROM : Hank Heijink (Mailinglists)
DATE : Thu Mar 06 22:12:13 2008

It's a little busy at the developer website, since they just announced 
the iPhone SDK. I think there's nothing to do but wait...

Best,
Hank

On Mar 6, 2008, at 4:05 PM, Joshua Preston wrote:

> 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
> Joshua.<email_removed>
>
>
>
>
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