SwiftData — Foundations Skill

Purpose

Route SwiftData implementation tasks to the minimum required SwiftData Knowledge Contracts. v1 scope is declaring @Model classes and their attributes/relationships, setting up and injecting a ModelContainer, performing CRUD through a ModelContext, fetching with @Query or FetchDescriptor, and delete-rule/referential-integrity behavior on relationships -- not CloudKit sync, not schema migration, not Core Data interop, and not the #Index/#Unique macros beyond a basic mention.

Routing

Load only the contracts relevant to the task. All paths relative to knowledge/swiftdata/.

• Annotating a class with @Model; customizing a property with @Attribute (e.g. .unique) or @Transient; declaring a @Relationship property and its inverse:; or asking what SwiftData auto-synthesizes (Identifiable/Hashable/Observable, not Codable) -> model-definition.md
• Setting up .modelContainer(for:)/.modelContainer(_:); configuring ModelConfiguration (isStoredInMemoryOnly, allowsSave); creating a ModelContainer(for:configurations:) manually for previews/tests/non-SwiftUI code; or wiring @Environment(\.modelContext) -> model-container-setup.md
• Calling context.insert(_:)/delete(_:)/save(); deciding whether autosaveEnabled makes an explicit save() unnecessary; choosing mainContext vs. a manually created secondary ModelContext; or enabling undo via context.undoManager -> model-context-crud.md
• Fetching with @Query (filter:/sort:/order:/animation:) in a SwiftUI view; building a #Predicate; or fetching outside a view with FetchDescriptor<Model> + context.fetch(_:) -> querying-with-query-and-fetchdescriptor.md
• Choosing a @Relationship(deleteRule:) value (.cascade/.nullify/.deny/.noAction); reasoning about what happens to related models on delete; or diagnosing a one-directional relationship missing its inverse: -> relationships-and-cascade-delete.md

Never load more than the contracts relevant to the specific question.

Stop Conditions

Stop and report if the requested topic has no matching Knowledge Contract in knowledge/swiftdata/ — do not guess or fall back to general knowledge. CloudKit sync integration (ModelConfiguration(cloudKitDatabase:)) is out of scope entirely -- not built as a contract here. Schema migration (SchemaMigrationPlan, VersionedSchema, lightweight vs. custom migration) is out of scope entirely -- not yet built. Core Data interop or migration (NSManagedObjectContext, NSFetchRequest) belongs to a separate Core Data domain, not this one -- do not answer Core Data questions from SwiftData contracts or fabricate a shared API surface. The #Index/ #Unique freestanding macros beyond the basic @Attribute(.unique) case, and SwiftData in widget extensions or App Group container sharing, are out of scope entirely -- report the boundary rather than fabricate behavior.