To define a new entity object from your data model screen. Click the entity object (following screen)
Deviceauth is name of entity selected here, to create an object of this entry,
Click the option that says create NSManagedObject class. X-Code will create the header and implementation file for you.
When you update CoreData data model there is always an error "The model used to open the store is incompatible with the one used to create the store",
Solution to solve this error
Delete the app from simulator/test device and run build program to install again.
Saves a lot of time.