Xcode-beta 8. Can't create core data

Question

I have been trying to add core data. And every time I got the same error:

error: filename "EntityName +CoreDataClass.swift" used twice: '/Users/userName/Desktop/Development/MyApp/AppName/EntityName +CoreDataClass.swift' and '/Users/userName/Library/Developer/Xcode/DerivedData/AppName-dgwzrmxsetzvtedibxrazuutjwnh/Build/Intermediates/AppName.build/Debug-iphoneos/AppName.build/DerivedSources/CoreDataGenerated/Model/EntityName +CoreDataClass.swift' 

I add core data using the following steps:
1.New file/ DataModel; save it in the root dir of my project
select Model.xcdatamodeld and add entity, add several attributes, save, editor/create NSManagedObjectClass Subclass.

As a result I observe 4 new files in navigator: Model.xcdatamodeld, EntityName+CoreDataProperties.swift, EntityName +CoreDataClass.swift, _COREDATA_DATAMODELNAME_+CoreDataModel.swift

their content: _COREDATA_DATAMODELNAME_+CoreDataModel.swift:

import Foundation import CoreData  ___COREDATA_DATAMODEL_MANAGEDOBJECTCLASSES_IMPLEMENTATIONS___ 

EntityName +CoreDataClass.swift:

import Foundation import CoreData   class EntityName: NSManagedObject {  } 

EntityName+CoreDataProperties.swift:

import Foundation import CoreData  extension EntityName {      @nonobjc class func fetchRequest() -> NSFetchRequest< EntityName > {         return NSFetchRequest< EntityName >(entityName: "EntityName");     }      @NSManaged var str: String?  } 

What I have tried:
1. Clean build, remove DerivedData, delete content of var/folders, restart
2. Delete generated files, displayed in navigator

All my efforts were out of luck.
What I am doing wrong?

Answer 1

There are two bugs in XCode 8 here:

1 - If you change the Codegen dropdown, it's new value isn't saved in Model.xcdatamodel. You have to change something else to get it to save. For example change the class name; build; change the class name back; build again.

2 - The generated code is placed in DerivedData in the Intermediates folder, but it only happens if the folder doesn't already exist. The workaround is to do a clean then a build.

Answer 2

Xcode 8 includes automatic NSManagedObject class generation when the model file uses the Xcode 8 file format. If you create your own subclass files, you're creating duplicates. The second file in the error message, in DerivedSources, is the one that Xcode created automatically.

If the automatically generated files do what you need, just stop creating your own and you'll be OK.

If you want to create your own subclasses instead, you can either

• Set the "tools version" for the model file to be Xcode 7.3 or earlier to disable all code generation (this doesn't seem to change anything meaningful about the actual file contents), or
• Disable automatic generation for each entity individually by setting the "Codegen" setting to "Manual/None" for the entity.