Duplicate Symbol Error in NSManagedObject Subclass

by

You are generating files which have already been generated for you by Xcode and thus get duplicate declarations. Details about this feature (new in Xcode 8) can be found in this WWDC video.

Two possible fixes:

1) Use the Xcode generated ManagedObject subclasses (the recommended, modern approach)

  • Delete all generated NSManagedObject subclasses from your project, if exists.
  • Set Codegento Class Definition in your .xcdatamodel for all entities
  • Make sure Module is empty (“Global Namespace” in light gray) (workaround an Apple bug, see this answer)

Note:

Never add the automatically generated files to your project. Even you do not see the generated files in your project, Xcode has a reference to it, so you are able to write extensions and such. For instance:

extension MyEntity {
    func doSomething() {
        //
    }
}

Also, you can command+click to the generated file within Xcode.

2) Trigger subclass generation manually (a rather paranoid but bullet-prove approach, ignoring the new Xcode features)

  • Delete all generated NSManagedObject subclasses from your project, if exists.
  • Set Codegento Manual/None in your .xcdatamodel for all entities
  • Clean project
  • Clean DerivedData folder
  • Restart Xcode
  • Manually generate NSManagedObject subclasses (in “Editor” menu)
  • Make sure those files are added to your project
  • build

More Related Contents:

  1. Unable to find specific subclass of NSManagedObject
  2. Sqlite File Location Core Data
  3. How do I make an HTTP request in Swift?
  4. Instantiate and Present a viewController in Swift
  5. Delete/Reset all entries in Core Data?
  6. Save images in NSUserDefaults?
  7. UIImageView – How to get the file name of the image assigned?
  8. How to share an image on Instagram in iOS?
  9. MKMapView: Instead of Annotation Pin, a custom view
  10. Detect current device with UI_USER_INTERFACE_IDIOM() in Swift
  11. UITapGestureRecognizer – make it work on touch down, not touch up?
  12. How to modify SWIFT_MODULE_NAME?
  13. ViewDidAppear is not called when opening app from background
  14. Xcode NSManagedObject subclass contains optionals when they are marked as non-optional
  15. Add bottom border line to UI TextField view in SwiftUI / Swift / Objective-C / Xamarin
  16. Positioning UITabBar at the top
  17. UITableViewCell with dynamic height iOS
  18. How to store an image in core data
  19. NSDate – Convert Date to GMT
  20. How to add a button to the MKPointAnnotation?
  21. SwiftUI DatePicker Binding optional Date, valid nil
  22. Swift performSelector:withObject:afterDelay: is unavailable [duplicate]
  23. When to use takeUnretainedValue() or takeRetainedValue() to retrieve Unmanaged Objects in Swift?
  24. Xcode 9 – failed to emit precompiled header [duplicate]
  25. ‘Receiver () has no segue with identifier ‘addSegue’
  26. How shouldChangeCharactersInRange works in Swift?
  27. UIView’s border color in Interface builder doesn’t work?
  28. AutoLayout views make app crash on popViewController
  29. Accessing Core Data Stack in MVVM application
  30. How to properly group a list fetched from CoreData by date?

Leave a Comment