Core Data Codegen Explained!

No more head-scratching

Starting from Xcode8, Apple has added a new Codegen setting in the Xcode data model editor to help developer manage and maintain their NSManagedObject subclasses. The Codegen setting consist of 3 possible configurations:

• Manual/None
• Class Definition
• Category/Extension

These 3 configurations might look a bit confusing at first, and I found out that it is actually quite difficult to find a good article that explain the differences between each configuration and which one to use.

In this article I will go through each configuration and analyse the differences between each of them and I will also give some suggestion on which one you should use and how you should use it for your Core Data project. Without further ado let’s get started!

Manual/None

This is the default behaviour prior to Xcode8 where developer have to manually create and maintain the changes of the NSManagedObject subclasses.

You can try to create a sample core data project, add a new entity call TestEntity and generate NSManagedObject subclass following the step in this link.

If you follow the step correctly, Xcode will generate 2 files: