Re: Using NSFetchRequest to fetch NSManagedObject subclasses
Re: Using NSFetchRequest to fetch NSManagedObject subclasses
- Subject: Re: Using NSFetchRequest to fetch NSManagedObject subclasses
- From: Matt James <email@hidden>
- Date: Sat, 10 Jul 2010 01:07:57 -0400
Wow, thank you so much. I have no idea how I missed the "Class" column in the xcdatamodel's UI. From what I saw, none of the tutorials mentioned doing this either. Maybe I was reading the newbie stuff where they didn't get into fun stuff like that.
Again, thanks a TON!
-Matt
On Jul 10, 2010, at 12:57 AM, Roland King wrote:
> Your model (xcdatamodel) says what class is used for each entity, you have that set to the name of your custom class, right? If so it will give you the correct object type when you insert or retrieve it.
>
> executeFetchRequest:error: in NSManagedObjectContext will return an NSArray() of the correct subclasses of NSManagedObject. If you're using methods which are documented to return NSManagedObject*(s) [ can't think of one offhand ] that should also be actually returning the correct subclass, you just need to cast.
>
> On 10-Jul-2010, at 12:29 PM, Matt James wrote:
>
>> Hi all,
>>
>> In the WWDC session "Mastering Core Data", it was recommended to subclass NSManagedObject, which I'm doing. Not only does this follow their recommendation, but it's also helpful for coding additional logic that might be appropriate on a per-model basis. What I don't understand, however, is how to fetch those subclassed objects from the managed object context.
>>
>> As an example, let's say I have PersonModel which extends NSManagedObject and, for me, represents a "Person" entity. When I run a fetch for Person entities, I get back NSManagedObjects. That's fine, but I'm unable to make use of any custom logic I have on the PersonModel class.
>>
>> I'm new to Core Data, so I may very well be misunderstanding the recommendations or be doing things in a screwy manner. Please straighten me out!
>>
>> Thanks for any help.
>>
>> -Matt James
>> http://www.macyenta.com_______________________________________________
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