# Swiftdata

> Route SwiftData implementation tasks to the correct Knowledge Contracts -- declaring persistent model classes with @Model/@Attribute/@Relationship/@Transient, creating and injecting a ModelContainer/ModelConfiguration via .modelContainer, ModelContext CRUD (insert/delete/save/autosave/undo), fetching with @Query or FetchDescriptor+context.fetch(_:), and @Relationship(deleteRule:) referential integrity. Use when writing @Model class RemoteImage { ... }, @Attribute(.unique), @Relationship(deleteRule:inverse:), @Transient, ModelContainer(for:configurations:), ModelConfiguration(isStoredInMemoryOnly:), .modelContainer(for:)/.modelContainer(_:), @Environment(\.modelContext), context.insert(_:)/delete(_:)/save(), context.autosaveEnabled, context.undoManager, @Query(filter:sort:order:),

- Skill: `caglarbaranbora/swiftdata` (Agent Skill)
- Install (CLI): `npx skillmds@latest add caglarbaranbora/swiftdata`
- Raw SKILL.md: https://api.skillmd.com/api/skills/caglarbaranbora/swiftdata/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: AI & ML
- Author: caglarbaranbora (https://skillmd.com/u/caglarbaranbora)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/caglarbaranbora/swiftdata

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# 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.