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Swift language patterns and best practices including concurrency, performance, and modern idioms. Use for Swift language-level code review or architecture guidance.
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Based on SOC occupation classification
| name | swift-development |
| description | Swift language patterns and best practices including concurrency, performance, and modern idioms. Use for Swift language-level code review or architecture guidance. |
| allowed-tools | ["Read","Glob","Grep"] |
| last_verified | "2026-07-16T00:00:00.000Z" |
| review_by | "2027-06-22T00:00:00.000Z" |
| os_version | iOS 27 / macOS 27 |
Swift language-level guidance that applies across all Apple platforms.
Use this skill when the user:
Swift concurrency architecture and patterns.
nonisolated(nonsending), Apple's adoption doctrine)Swift 6.2 concurrency updates reference — the what-changed view (async-stays-on-caller, default MainActor inference, isolated conformances, @concurrent) with migration steps from 6.0/6.1 and top mistakes. Overlaps concurrency-patterns/swift62-concurrency.md by design: use this file when the question is "what changed in 6.2?", use concurrency-patterns when building or reviewing async code.
Complexity and size limits for Swift code — SwiftLint threshold rules (cyclomatic complexity, function/type/file length, parameter count) with a violations-baseline adoption path so existing code never blocks. Part of the deterministic gauntlet with testing/fitness-functions and testing/coverage-ratchet.
InlineArray, Span, and the Swift performance cost model.
swift-performance.md: the cost model — allocation, ARC/retain-release, exclusivity checks, dispatch, generics vs existentials, closures, ~Copyable ownershipTDD and testing skills for iOS/macOS apps. Covers characterization tests, TDD workflows, test contracts, snapshot tests, test infrastructure, and deterministic quality gates (fitness functions, coverage ratchet, mutation testing). Use for test-driven development, adding tests to existing code, or building test infrastructure.
Set up SwiftUI visual regression testing with swift-snapshot-testing. Generates snapshot test boilerplate and CI configuration. Use for UI regression prevention.
Gate test coverage with a ratchet — a committed baseline that coverage may never drop below and only ever rises. Ships a coverage-gate script (xccov-based) plus an advisory CRAP report (complexity × uncovered). Use when agent-written code needs a deterministic "tests were actually written" check.
Enforce complexity and size limits on Swift code with SwiftLint threshold rules — cyclomatic complexity, function/type/file length, parameter count — adopted via a violations baseline so existing code never blocks. Use when agent-written code needs deterministic size constraints.
Write architecture fitness functions — deterministic tests that enforce a project's hard rules (module boundaries, offline guarantees, content contracts) from inside its own test target. Use when a constraint lives only in prose (CLAUDE.md, code review) and should become un-arguable.
EXPERIMENTAL — mutation testing with muter to measure whether tests actually assert anything: mutants that survive reveal assertion-free coverage. Advisory report only, never a merge gate. Use on engine/logic targets when coverage numbers look good but bugs still slip through.