Re: Recomputing non-standard Core Data attributes when child MOC is saved?
Re: Recomputing non-standard Core Data attributes when child MOC is saved?
- Subject: Re: Recomputing non-standard Core Data attributes when child MOC is saved?
- From: Dave Fernandes <email@hidden>
- Date: Wed, 19 Jun 2013 11:29:44 -0400
On 2013-06-19, at 3:21 AM, Rick Mann <email@hidden> wrote:
>
> On Jun 18, 2013, at 22:42 , Dave Fernandes <email@hidden> wrote:
>
>> The foolproof way to do it is to have the transient attributes recalculated each time they are accessed. In other words, they are simply getter methods. But if they are expensive to compute, this might not work well. If you are using bindings or KVO, you then have a class method + (NSSet*)keyPathsForValuesAffecting<AttributeName> that ensures observers of the transient attribute are notified when underlying non-transient attributes change.
>
> In this case, it's not accessed terribly frequently, so that's what I ended up doing. I do use KVO a lot, although I don't see how that helps in this case (to trigger re-computing the transient value).
It's not useful if you want to pre-compute and cache the transient values. It is just useful if the transient is a getter, and you need to notify the observers.
>
> Pity there's not an update method that can be overridden in NSManagedObjectSubclasses when this happens. I guess my objects could KVO themselves…
>
> --
> Rick
>
>
>
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