Re: Core Data Conundrum
Re: Core Data Conundrum
- Subject: Re: Core Data Conundrum
- From: Rick Mann <email@hidden>
- Date: Sat, 12 Dec 2009 16:50:02 -0800
I'm not sure that's actually a solution. The problem is that if I can specify a relationship and its inverse in the Core Data model editor, then Core Data handles setting the opposite end of the relationship for me. Since this is a generic feature, it can't do what I want, because adding a Segment to a Node has an ambiguous inverse.
I think the solution is to mark the relationships as not having inverses in the model, and then manage the inverse relationship myself in code (that is, always require that a Node be set on a Segment, and that operation will then add the Segment to the Node).
Can anyone confirm that this is indeed how to solve this problem? Thanks!
On Dec 12, 2009, at 16:43:02, Charlie Dickman wrote:
> Rick,
>
> This can be done in a straightforward manner using C structures that contain pointers to the C structures.
>
> For example, you can define structures
>
> typedef node _node {
> segment *someSegment;
> }
>
> typedef struct _segment {
> node node1;
> node node2;
> }
>
> set node.segment to nil in the last segment and chain them together. Remember to malloc each instance and free them when they are no longer needed.
>
> This model can easily be transmogrified into Objective C objects.
>
> On Dec 12, 2009, at 7:30 PM, Rick Mann wrote:
>
>> Hi. I'm trying to set up a model for a Node and a Segment. A Segment exists between Nodes. Each Segment has a node1 and node2 attribute, and each Node can have multiple Segments. I don't seem to be able to model this relationship; I can have either node1 with an inverse of segments, or node 2, but not both.
>>
>> It's important for me to distinguish which end of a segment a particular Node is associated with (imagine drawing a directed arrow). I feel like this should be straightforward, but I'm stuck.
>>
>> Any suggestions?
>>
>> TIA,
>> Rick
>>
>> _______________________________________________
>>
>> Cocoa-dev mailing list (email@hidden)
>>
>> Please do not post admin requests or moderator comments to the list.
>> Contact the moderators at cocoa-dev-admins(at)lists.apple.com
>>
>> Help/Unsubscribe/Update your Subscription:
>>
>> This email sent to email@hidden
>
> Charlie Dickman
> email@hidden
>
>
>
_______________________________________________
Cocoa-dev mailing list (email@hidden)
Please do not post admin requests or moderator comments to the list.
Contact the moderators at cocoa-dev-admins(at)lists.apple.com
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden