Core Data and SwiftData, as powerful persistence frameworks in the Apple ecosystem, not only provide declarative data listening tools like @FetchRequest and @Query, but also have a complete set of data tracking and notification mechanisms built-in. Understanding and mastering these mechanisms is crucial for building robust data-driven applications. This article will take you through multi-layered solutions—from simple custom notifications to the powerful Persistent History Tracking and SwiftData History—to help you handle various complex data synchronization scenarios.