Re: Core Data Implementation question
Re: Core Data Implementation question
- Subject: Re: Core Data Implementation question
- From: "Marcus S. Zarra" <email@hidden>
- Date: Wed, 20 Jul 2005 14:58:04 -0600
Thanks for the link, I will be looking into that. In this situation the
derived value is derived from values that are inside of the children and it
occurs after the children are first created. In other words the method does
the following:
1. Generate a new child
2. Set values inside of that child
3. Add child to parent
4. ???
5. Notify the GUI to update the other fields.
Step 4 and 5 are a mystery to me at this point. :)
Marcus
On 7/20/05, Charilaos Skiadas <email@hidden> wrote:
>
> On Jul 20, 2005, at 12:03 PM, Marcus S. Zarra wrote:
>
> I am trying to figure out the best way to approach this issue with Core
> Data.
>
> I have a parent object that has a to-many relationship with a child
> object.
> The child has a to-one relationship with the parent.
>
> Parent <-->> Child
>
> Adding new children works correctly and the GUI (which displays the
> children
> in a table) works perfectly.
>
> The problem comes in with a couple of attributes in the parent. The parent
> has a couple of values that are changed based on the children. The
> children
> are added progammatically and I need a way to notify any observers that
> the
> parent attributes have changed when I add the child. I have tried doing
> the
> following:
>
>
> Are the values only changing when a child is added? In that case, you
> should I think be able to just use the "derived value" approach described in
>
>
> http://developer.apple.com/documentation/Cocoa/Conceptual/NSPersistentDocumentTutorial/03_CustomClass/chapter_4_section_3.html#//apple_ref/doc/uid/TP40001799-CH219-DontLinkElementID_14
>
> and the the "children" key as the key in the "initialize" method that
> triggers the notification.
>
> If on the other hand the attributes depend on attributes in the children
> themselves, then I am not too sure what the best way to accomplish that is,
> but I sure would like to know.
>
> [parent willChangeValueForKey:@"xxx"];
> //add child
> [parent didChangeValueForKey:@"xxx"];
>
> but this seems to mess up the actual update of the child.
>
> Does anyone know of a cleaner way to get this to work? Note that the
> parent
> attribute "xxx" is a calculated value in the parent object and not a value
> stored in the core data repository.
>
> Thanks for any insight.
>
> Marcus S. Zarra
>
>
> Haris
>
>
>
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