Exception thrown in NSOrderedSet generated accessors

Question

On my Lion app, I have this data model:

The relationship subitem

Answer 1

The Apple docs To Many Relations says: you should access the proxy mutable set or ordered set using

NSMutableOrderedSet * set = [managedObject mutableOrderedSetValueForKey:@"toManyRelation"];

Modifying this set will add or remove relations to your managed object. Accessing the mutable ordered set using the accessor whether with [ ] or . notation is wrong and will fail.