Core Data: Rename Attribute Without Having Issues with Users and Their Current Data

Is it possible to add a new attribute to Core Data without having issues with users and their current data?

The process is called Core Data Migration: Ray Wenderlich has a great tutorial on it here. If you are just adding a new attribute, it should be (relatively) simple to do an automatic/lightweight migration.

Rename Core Data Entity without Loss of Data

Posting here for anyone else who needs to rename CoreData Entities (in order to avoid conflicts with SwiftUI reserved names).

Change the name of the class name for the entity (under Class in the Data Model Inspector), but do not change the name of the Entity.

You'll now have to change the name of the entity used throughout the code to the new updated class name. (FileImage -> Image), but the CoreData will no longer be in conflict with the SwiftUI reserved keyword, while maintaining all your data.

Problem with Core Data, after a rename of the app?

In a terminal navigate into the project directory and actually cd into the .xcodeproj file itself. Edit the project.pbxproj file with vi and change all the occurrences of the former name to the updated one. It seems that Xcode doesn't know to update all of the Core Data references, but this worked for me.

Core Data attribute crawling as nil after renaming, even after I changed the name back

If you don't want to add migration, just remove and install the App.

But if you want to rename a property in already published App than you need to add lightweight migration.

Changing an attribute in CoreData gives me NSCocoaErrorDomain Code=134140

The error comes because of a mismatch between the stored database file, where you have a string, and what you've told Core Data is in there, which is now an Int. You refer to a mapping model problem but it doesn't sound like you've used a mapping model at all, just changed the model definition directly and expected the framework to cope.

If this is an early stage app (i.e you're still developing the first version) just delete the app from the device or simulator and re-run once you've changed the model and class definition files.

If your app is out in the wild and on user devices, and you don't care about keeping the data, you'll need to include some code to delete the database file on startup according to some defaults key that you define.

If you want to keep the data, then you need to create a new model version in the core data model editor, where the type is defined how you like it, and then add migration or mapping rules to define what should happen during the conversion - I don't think there is any automatically inferrable mapping rule to turn any string into an integer.

Renaming a CoreData Entity, representedClassName does not get renamed

select the entity and check the entity inspector in the utilities view's data model inspector (the left left menu), each entity has a name field and a class field. When you change the name in the GUI you only change the class name. To correct the error you to change the name as well.

Cannot retrieve renamed attribute's value in Core Data

If you want to rename an attribute and keep the old data, there are two things you need to do:

1. Create a new version of the data model. You probably already did this, or your app would not have been able to load the old data at all. If not though, make sure you keep your changes in a different version of the model file. The old model version needs to be available or migration won't work.

2. On this property, set the "renaming identifier" field to contain the old name of the attribute. This will tell Core Data that it should migrate values to the new attribute name. Without that it can't tell if you want to rename the attribute or if you want to delete the old one and add a new, different attribute. In the model editor, you'll find this on the right when you select the new attribute:

You may find Apple's guide to lightweight migration to be useful too.

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