axiom-swiftdata

# SwiftData

## Overview

Apple's native persistence framework using `@Model` classes and declarative queries. Built on Core Data, designed for SwiftUI.

**Core principle** Reference types (`class`) + `@Model` macro + declarative `@Query` for reactive SwiftUI integration.

**Requires** iOS 17+, Swift 5.9+
**Target** iOS 26+ (this skill focuses on latest features)
**License** Proprietary (Apple)

## When to Use SwiftData

#### Choose SwiftData when you need
- ✅ Native Apple integration with SwiftUI
- ✅ Simple CRUD operations
- ✅ Automatic UI updates with `@Query`
- ✅ CloudKit sync (iOS 17+)
- ✅ Reference types (classes) with relationships

#### Use SQLiteData instead when
- Need value types (structs)
- CloudKit record sharing (not just sync)
- Large datasets (50k+ records) with specific performance needs

#### Use GRDB when
- Complex raw SQL required
- Fine-grained migration control needed

**For migrations** See the `axiom-swiftdata-migration` skill for custom schema migrations with VersionedSchema and SchemaMigrationPlan. For migration debugging, see `axiom-swiftdata-migration-diag`.

## Example Prompts

These are real questions developers ask that this skill is designed to answer:

#### Basic Operations

#### 1. "I have a notes app with folders. I need to filter notes by folder and sort by last modified. How do I set up the @Query?"
→ The skill shows how to use `@Query` with predicates, sorting, and automatic view updates

#### 2. "When a user deletes a task list, all tasks should auto-delete too. How do I set up the relationship?"
→ The skill explains `@Relationship` with `deleteRule: .cascade` and inverse relationships

#### 3. "I have a relationship between User → Messages → Attachments. How do I prevent orphaned data when deleting?"
→ The skill shows cascading deletes, inverse relationships, and safe deletion patterns

#### CloudKit & Sync

#### 4. "My chat app syncs messages to other devices via CloudKit. Sometimes messages conflict. How do I handle sync conf