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twostrawstwostraws/SwiftData-Agent-Skill/swiftdata-pro/SKILL.md

swiftdata-pro

Skill452 starsChanged 8 months agoMITView on GitHub

Writes, reviews, and improves SwiftData code using modern APIs and best practices. Use when reading, writing, or reviewing projects that use SwiftData.

We split this skill into the rules it gives an agent

11 rules. About 0 are common, 6 are distinctive, and 5 are very specific to this project.

  • ≈0

    Common · estimate

    Many files like this have a rule of this kind.

  • ≈6

    Distinctive · estimate

    This author's own choices. Worth a look.

  • 5

    Very specific

    Tied to their project's names, files or tools. Probably skip.

  • Common
  • Distinctive
  • Very specific
  1. Distinctive:

    Write and review SwiftData code for correctness, modern API usage, and adherence to project conventions.

    line 10
  2. Very specific:

    Check for core SwiftData issues using references/core-rules.md.

    line 14
  3. Very specific:

    Check that predicates are safe and supported using references/predicates.md.

    line 15
  4. Very specific:

    If the project uses CloudKit, check for CloudKit-specific constraints using references/cloudkit.md.

    line 16
  5. Very specific:

    If the project targets iOS 18+, check for indexing opportunities using references/indexing.md.

    line 17
  6. Very specific:

    If the project targets iOS 26+, check for class inheritance patterns using references/class-inheritance.md.

    line 18
  7. Distinctive:

    If doing partial work, load only the relevant reference files.

    line 20
  8. Distinctive:

    Do not introduce third-party frameworks without asking first.

    line 27
  9. Distinctive:

    Use a consistent project structure, with folder layout determined by app features.

    line 28
  10. Distinctive:

    If the user asks for a review, organize findings by file.

    line 33
  11. Distinctive:

    If the user asks you to write or improve code, follow the same rules above but make the changes directly instead of returning a findings …

    line 41

≈ “Common” is an estimate: at least 1 in 5 of the 308,232 skill files we read have a rule of the same kind, not the same words. “Very specific” is our guess from the words: it names a file, a command, a setting or the project itself.

Keep what fits and drop the rest. Your version, ready for your agents.
Files
SKILL.md

Write and review SwiftData code for correctness, modern API usage, and adherence to project conventions. Report only genuine problems - do not nitpick or invent issues.

Review process:

  1. Check for core SwiftData issues using references/core-rules.md.
  2. Check that predicates are safe and supported using references/predicates.md.
  3. If the project uses CloudKit, check for CloudKit-specific constraints using references/cloudkit.md.
  4. If the project targets iOS 18+, check for indexing opportunities using references/indexing.md.
  5. If the project targets iOS 26+, check for class inheritance patterns using references/class-inheritance.md.

If doing partial work, load only the relevant reference files.

Core Instructions

  • Target Swift 6.2 or later, using modern Swift concurrency.
  • The user strongly prefers to use SwiftData across the board. Do not suggest Core Data functionality unless it is a feature that cannot be solved with SwiftData.
  • Do not introduce third-party frameworks without asking first.
  • Use a consistent project structure, with folder layout determined by app features.

Output Format

If the user asks for a review, organize findings by file. For each issue:

  1. State the file and relevant line(s).
  2. Name the rule being violated.
  3. Show a brief before/after code fix.

Skip files with no issues. End with a prioritized summary of the most impactful changes to make first.

If the user asks you to write or improve code, follow the same rules above but make the changes directly instead of returning a findings report.

Example output:

Destination.swift

Line 8: Add an explicit delete rule for relationships.

// Before
var sights: [Sight]

// After
@Relationship(deleteRule: .cascade, inverse: \Sight.destination) var sights: [Sight]

Line 22: Do not use isEmpty == false in predicates – it crashes at runtime. Use ! instead.

// Before
#Predicate<Destination> { $0.sights.isEmpty == false }

// After
#Predicate<Destination> { !$0.sights.isEmpty }

DestinationListView.swift

Line 5: @Query must only be used inside SwiftUI views.

// Before
class DestinationStore {
    @Query var destinations: [Destination]
}

// After
class DestinationStore {
    var modelContext: ModelContext

    func fetchDestinations() throws -> [Destination] {
        try modelContext.fetch(FetchDescriptor<Destination>())
    }
}

Summary

  1. Data loss (high): Missing delete rule on line 8 of Destination.swift means sights will be orphaned when a destination is deleted.
  2. Crash (high): isEmpty == false on line 22 will crash at runtime – use !isEmpty instead.
  3. Incorrect behavior (high): @Query on line 5 of DestinationListView.swift only works inside SwiftUI views.

End of example.

References

  • references/core-rules.md - autosaving, relationships, delete rules, property restrictions, and FetchDescriptor optimization.
  • references/predicates.md - supported predicate operations, dangerous patterns that crash at runtime, and unsupported methods.
  • references/cloudkit.md - CloudKit-specific constraints including uniqueness, optionality, and eventual consistency.
  • references/indexing.md - database indexing for iOS 18+, including single and compound property indexes.
  • references/class-inheritance.md - model subclassing for iOS 26+, including @available requirements, schema setup, and predicate filtering.

Download now (ZIP)

  • Other versions5 projects use a version of this.

    Word for word · 3

    1. Provenance-Emu/Provenance★ 6.4k100% same
    2. 199-biotechnologies/swiftui-claude-skills★ 7100% same
    3. kelvinkosbab/KozBon★ 5100% same

    Wrote their own version · 0

    None found.

    How matches are found. Word for word: the exact same text. Edited: shares passages with this file (“99% same” means 99% of its five-word phrases also appear here; 10% or more counts). Their own version: similar meaning, or, weakest, the same name. We can’t tell which project had it first. Projects are counted among the 200 most-starred candidates, and mentions are links to the repository we found, up to 50 per site, so both counts are a floor.

  • Used alongsideProjects with it also use swift-concurrency-pro, swiftui-pro and 1 more.

    Other files people use alongside this one.

    Files found in the same public projects as a version of this one, more often than they turn up anywhere else. Each project counts once, large collections count for less, and this file's own repository is left out.
    • twostrawsSkill

      swift-concurrency-pro

      Reviews Swift code for concurrency correctness, modern API usage, and common async/await pitfalls. Use when reading, writing, or reviewing Swift concurrency code.

      Also in 4 projects that use this

    • kingsidharthSkill

      swiftui-pro

      Comprehensively reviews SwiftUI code for best practices on modern APIs, maintainability, and performance. Use when reading, writing, or reviewing SwiftUI projects.

      Also in 4 projects that use this

    • jamesrochabrunSkill

      swift-concurrency

      Guide for building, auditing, and refactoring Swift code using modern concurrency patterns (Swift 6+). This skill should be used when working with async/await, Tasks, actors, MainActor, Sendable types, isolation domains, or when migrating legacy callback/Combine code to structured concurrency. Covers Approachable Concurrency settings, isolated parameters, and common pitfalls.

      Also in 3 projects that use this

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