Subclassing NSManagedObject with swift 3 and Xcode 8 beta

core-datansmanagedobjectswift3xcode8

I've began to try use Core data with swift 3 and Xcode 8 beta. When I try to generate NSManagedObject subclasses from core data model and Create NSManagedObject subclass… option in Editor menu, Xcode 8 beta generates three files one of them is _COREDATA_DATAMODELNAME_+CoreDataModel.swift with the following content:

import Foundation
import CoreData

___COREDATA_DATAMODEL_MANAGEDOBJECTCLASSES_IMPLEMENTATIONS___

In addition, the content of this file shows two warnings:

Expressions are not allowed at the top level.
Use of unresolved identifier '___COREDATA_DATAMODEL_MANAGEDOBJECTCLASSES_IMPLEMENTATIONS___'

Has anyones faced the same issue? Which is the meaning of this new file?

Thanks

Best Answer

It's probably a (beta) clash with the new automatic subclass generation, which can be controlled in the entity inspector of the data model file.

From the documentation (What's New In Core Data)

Xcode automatic subclass generation

Xcode now supports automatic generation of NSManagedObject subclasses in the modeling tool. In the entity inspector:

Manual/None is the default, and previous behavior; in this case you should implement your own subclass or use NSManagedObject.

Category/Extension generates a class extension in a file named like ClassName+CoreDataGeneratedProperties. You need to declare/implement the main class (if in Obj-C, via a header the extension can import named ClassName.h). -

Class Definition generates subclass files named like ClassName+CoreDataClass as well as the files generated for Category/Extension.

The generated files are placed in DerivedData and rebuilt on the first build after the model is saved. They are also indexed by Xcode, so command-clicking on references and fast-opening by filename works.

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This warning is one of the quirks we have to deal with while the details of the Swift implementation are being ironed out. The warning occurs spuriously, i.e. your setup might work even if you do not follow the steps outlined below.

I have been able to get rid of it in most cases by making sure that the class is set correctly in the model editor. Unlike in many other SOF posts (including answers to this question), the suggestion to include the module name (like MyApp.Shows) has not helped me.

Make sure you check these three items:

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Version that works up to Xcode 7 beta 3

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Notice that I corrected your entity name to the more appropriate singular.

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Best Answer

Xcode automatic subclass generation

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