Setting an NSManagedObject relationship in Swift

As of Xcode 7 and Swift 2.0 (see release note #17583057), you are able to just add the following definitions to the generated extension file:

extension PersonModel {
    // This is what got generated by core data
    @NSManaged var name: String?
    @NSManaged var hairColor: NSNumber?
    @NSManaged var parents: NSSet?

    // This is what I manually added
    @NSManaged func addParentsObject(value: ParentModel)
    @NSManaged func removeParentsObject(value: ParentModel)
    @NSManaged func addParents(value: Set<ParentModel>)
    @NSManaged func removeParents(value: Set<ParentModel>)
}

This works because

The NSManaged attribute can be used with methods as well as
properties, for access to Core Data’s automatically generated
Key-Value-Coding-compliant to-many accessors.

Adding this definition will allow you to add items to your collections. Not sure why these aren’t just generated automatically…