Agent Skills: SwiftData Code Review

SwiftData Code Review

Quick Reference

| Issue Type | Reference | |------------|-----------| | @Model, @Attribute, @Relationship, delete rules | references/model-design.md | | @Query, #Predicate, FetchDescriptor, #Index | references/queries.md | | @ModelActor, ModelContext, background operations | references/concurrency.md | | VersionedSchema, MigrationStage, lightweight/custom | references/migrations.md |

Hard gates (before reporting findings)

Run in order; do not assert an issue until the gate for that issue passes.

1. Scope — pass when: You have the target .swift path(s) and confirmed SwiftData surface in scope (e.g. import SwiftData, @Model, @Query, @ModelActor, VersionedSchema, or migration types). If none apply, stop or narrow scope with one sentence.
2. Reference — pass when: For each checklist area you evaluate (models, queries, concurrency, migrations), you opened the matching references/*.md from the Quick Reference table or wrote N/A: no <area> in this review with a one-line reason.
3. Evidence — pass when: Every finding uses the [FILE:LINE] ISSUE_TITLE header (line range allowed) from the file you read; no finding without a cite.
4. Report — pass when: Findings list cites first (or inline) using [FILE:LINE] ISSUE_TITLE, then severity or checklist grouping—no uncited assertions.

Review Checklist

• [ ] Models marked final (subclassing crashes)
• [ ] @Relationship decorator on ONE side only (not both)
• [ ] Delete rules explicitly set (not relying on default .nullify)
• [ ] Relationships initialized to empty arrays, not default objects
• [ ] Batch operations used for bulk inserts (append(contentsOf:))
• [ ] @Query not loading thousands of items on main thread
• [ ] External values in predicates captured in local variables
• [ ] Scalar comparisons in predicates (not object references)
• [ ] @ModelActor used for background operations
• [ ] PersistentIdentifier/DTOs used to pass data between actors
• [ ] VersionedSchema defined for each shipped version
• [ ] MigrationPlan passed to ModelContainer

When to Load References

• Reviewing @Model or relationships -> model-design.md
• Reviewing @Query or #Predicate -> queries.md
• Reviewing @ModelActor or background work -> concurrency.md
• Reviewing schema changes or migrations -> migrations.md

Review Questions

1. Could this relationship assignment cause NULL foreign keys?
2. Is @Relationship on both sides creating circular references?
3. Could this @Query block the main thread with large datasets?
4. Are model objects being passed between actors unsafely?
5. Would schema changes require a migration plan?