Configure Core Data stacks with NSPersistentContainer and background contexts.
npx skills add https://github.com/CharlesWiltgen/Axiom --skill core-data
Please help me install this Agent Skill. Skill: core-data Source: https://github.com/CharlesWiltgen/Axiom/tree/main/.claude-plugin/plugins/axiom/skills/core-data Command: npx skills add https://github.com/CharlesWiltgen/Axiom --skill core-data
Core Data patterns and concurrency guidance for when to use Core Data versus SwiftData, plus how to set up a robust Core Data stack.
Set up a basic Core Data stack with NSPersistentContainer and a background context.
High-intent search queries and answers about installing and using this skill.
Core Data remains the robust choice for complex persistence needs, especially with CloudKit syncing, concurrency demands, or iOS 15 support. SwiftData suits simpler data models on iOS 17+. Choose Core Data if you need advanced relationship modeling, migration control, or multi-user sync.
Initialize NSPersistentContainer, configure background contexts with proper concurrency types (privateQueueConcurrencyType for workers), and use perform() blocks to access data on the correct thread. This prevents thread-confinement violations that cause crashes in multi-threaded scenarios.
Enable automatic migrations via lightweight schema versioning when safe, configure merge policies for conflict resolution, and test migrations across your target iOS versions. Plan data transformations incrementally to avoid migration failures in production.
Yes, use NSPersistentCloudKitContainer instead of NSPersistentContainer to enable CloudKit sync. It handles schema mirroring and remote change merging automatically, reducing boilerplate for multi-device synchronization.
Define relationships in your data model using NSRelationshipDescription with cardinality settings (to-one or to-many) and inverse relationships for consistency. Many-to-many relationships require a join entity or use ordered NSSet properties for optimization.
Background contexts must be configured with privateQueueConcurrencyType and all fetches or updates must occur within perform() or performAndWait() blocks. Improper context hierarchy or direct main-thread access to background data causes data corruption and crashes.
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