how do i do a coredata migration?

To perform a Core Data migration, you can leverage the new features introduced in SwiftData. Here are the steps and relevant information from the WWDC sessions:

1. Adopt SwiftData: SwiftData provides a framework that simplifies building your app's model layer and persisting it across launches. It includes features for modeling, migration, schema management, and more. You can start by importing the SwiftData framework and decorating your models with the @Model macro.

   • What’s new in SwiftData (00:01:01)

2. Customize the Model Container: You can tailor the model container to fine-tune its data location and usage throughout the app. This includes customizing the URL of the data on disk, enabling/disabling autosave, and more.

   • What’s new in SwiftData (00:04:29)

3. Use the History API: SwiftData history provides a way to track changes in your data over time. This is useful for migrations as it allows you to know what models have been inserted, updated, or deleted. The history API records transactions containing metadata about all changes, which can be queried and processed.

   • Track model changes with SwiftData history (00:02:16)
   • What’s new in SwiftData (00:03:34)

4. Create Custom Data Stores: If you need to migrate to a different storage backend, you can create custom data stores. SwiftData allows you to define your own data store implementations, which can support features like migration, history tracking, and CloudKit sync.

   • Create a custom data store with SwiftData (00:05:40)
   • Platforms State of the Union (00:41:00)

5. Migrate from Core Data to SwiftData: If you are using Core Data and want to migrate to SwiftData, you can benefit from persistent history and migrate to SwiftData history instead. This allows you to track and manage changes efficiently.

   • Track model changes with SwiftData history (00:16:20)

By following these steps and utilizing the new features in SwiftData, you can effectively manage and migrate your Core Data models. For more detailed information, you can refer to the specific sessions mentioned above.