Core Data: traversing to-many relationships
Core Data: traversing to-many relationships
- Subject: Core Data: traversing to-many relationships
- From: email@hidden
- Date: Tue, 10 Oct 2006 18:14:07 +0200
Hi,
I have a question regarding to-many relationships in Core Data:
Some background:
For my software tracking application, I have three entities: Product,
Version and License. A product has a to-many relationship to Version
and a Version has a to-many relationship to License. Both
relationships have an inverse to-one relationship (every license
belongs to exactly one version and every version belongs to exactly
one product).
Product <---->> Version <---->> License
I have two table views: one showing the Products and another one that
should show all Licenses for the selected product in the other table
view. The array controller for the licenses is bound to the selection
in the products array controller. The Model Key Path for the
contentSet binding of the license array controller is set to
versions.licenses and the Controller Key to selection.
I'd expect core data to take the selected product, gather all its
versions and then gather all licenses for all those versions, but
this does not happen. Instead, I'm getting the following error:
Exception raised during posting of notification. Ignored.
exception: [<_NSFaultingMutableSet 0x16660810>
addObserver:forKeyPath:options:context:] is not supported. Key path:
licenses. I have checked this and the licenses relationship is
defined in the Version table.
When I'm having the secondary table view display the versions
belonging to the products in the first table view (the classic
example), everything works as expected in a master/detail interface.
So while traversing one to-many relationship works fine, it seems
like I'm missing something to have Core Data traverse two to-many
relationships at once.
While I have some ideas for workarounds, I'm still wondering why this
approach does not work.
Thanks in advance!
Peter
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