iPhone Core Data: Cascading delete across a many-to-one relationship

Question

I have two classes A and B with a many-to-one relationship from A to B (multiple A objects may reference the same B). The question is, if the delete rule on the A side is C

Answer 1

Here's a Swift 4 version of Lukas' answer:

public override func prepareForDeletion() {
    guard let department = department else { return }

    if department.employees.filter({ !$0.isDeleted }).isEmpty {
        managedObjectContext?.delete(department)
    }
}