问题
I have an entity (e.g. Employee) in a managed object model that is related to two other entities (e.g. Department and Team). Both relationships are one-to-many (i.e. an Employee must have one Department and one Team, Teams and Departments have many Employees). The two may or may not overlap (e.g. a team might be made up of employees from HR, Accounting & I.T. or it might jut consist of several employees from the one department).
Department <-->> Employee <<--> Team
I have two NSArrayControllers providing data for two NSTableViews, a Department table and a Team table. Employees can move between departments and between teams without any problems but I'm not sure how to delete (fire) the employee.
If I send either of the array controllers a remove message the employee is taken out of the team (for example) but left in the department and the object graph is in an inconsistent state. Even if I call the remove action on both controllers the object is not deleted - it is orphaned and just hangs around in limbo.
Originally I had the Department & Team relationships (of the Employee entity) set to a delete rule of Nullify but even changing one or both to cascade doesn't help.
Do I need to override the remove: action on the array controllers to actually delete the employee or am I missing something really obvious?
回答1:
The NSArrayController has two different behaviors when you're using Core Data. If it is configured to simply fetch objects directly from the managed object context, it will delete the objects when they are removed.
If you're binding the contentSet to another controller, like it sounds like you are in this case, the default behavior is to simply remove the object from the relationship. If you want to delete it, though, there is a "deletes object on remove" binding option, which will produce the result you want.
来源：https://stackoverflow.com/questions/1598728/how-do-i-delete-an-entity-when-removing-it-from-an-array-controller