We continue our series on “modern persistence” with an important topic: “callbacks.” Callbacks are little hooks into the lifecycle of your data model so that you can be notified or take action when something changes. We will first explore the “Active Record” pattern of callbacks, popularized by Ruby on Rails, and then see how we can improve upon them.

How does our SQL-based solution for persistence compare with modern SwiftData? We put things to the test by rebuilding our complex @FetchAll query using @Model and the @Query macro!

We finish a sneak peek of our upcoming Structured Queries library by showing how queries built with the library can be reused and composed together, and how we can replace all of the raw queries in our application with simpler, safer query builders.

We introduce a new feature to our reminders app: cover images for each reminders list. This pushes us to create a brand new database table to synchronize, and allows us to demonstrate how SQLiteData seamlessly handles binary blobs by converting them to CloudKit assets under the hood.

With our database migrated, it’s time to take the SyncEngine for a spin to see how it seamlessly synchronizes data to and from iCloud, how it resolves conflicts when records are edited and deleted from multiple devices, and even how records are synchronized from different versions of the application and database schema.

We show how to add iCloud synchronization to the persistence layer of an existing SQLite application by using SQLiteData. While SQLiteData’s CloudKit tools can be configured with a single line of code, one must still prepare their database schema to be compatible and durable when it comes to synchronizing across multiple devices and versions.