Why does insertNewObjectForEntityForName only return a NSManagedObject?

Question

I'm trying to move some RubyMotion code to Swift. So far it works. What I do not understand is why the following result can't be casted to the Document class:

var newObject : NSManagedObject 
  NSEntityDescription.insertNewObjectForEntityForName("Document", inManagedObjectContext:context) 
  as NSManagedObject

The insertNewObjectForEntityForName call returns an object of type NSManagedObject. But why doesn't insertNewObjectForEntityForName returns an object of type Document as specified by entity.managedObjectClassName ?

My Entity looks like this:

func DocumentEntity () -> NSEntityDescription {

    var entity = NSEntityDescription()
    entity.name = "Document"
    entity.managedObjectClassName = "Document"

    var property = NSAttributeDescription()
    property.name = "title"
    property.attributeType = NSAttributeType.StringAttributeType
    property.optional = false

    entity.properties = [property]

    return entity
}

class Document : NSManagedObject {
    @NSManaged var title : String
}

model = NSManagedObjectModel()
model.entities = [DocumentEntity()]

var store = NSPersistentStoreCoordinator(managedObjectModel: model)

Answer 1

Make sure you set the class name of you entity in the object model. The format is YourAppModule.YourClassName.