I'm assuming that you are using NSArrayControllers in your Interface
Builder nib/xib file...
Bind the Content Set for the rgb controller to the collection
controller's 'selection' with a model key path of whatever your
relationship is called (ie the to-many relationship in the collection
>From the xcdatamodel of a "Core Data Document-based Application", I have two
>entities...
1st one entity is a set of rgb values.
2nd the other entity is a collection of these sets.
... so the add button of the 1st entity should not be available until an object
of the 2
