Swift Development
Swift language-level guidance that applies across all Apple platforms.
When This Skill Activates
Use this skill when the user:
- Asks about Swift concurrency (async/await, actors, Sendable, TaskGroup)
- Needs help with Swift 6 strict concurrency migration
- Has data race or actor isolation errors
- Asks about InlineArray, Span, or low-level memory performance
- Wants to eliminate heap allocations or replace unsafe pointers
- Asks about modern Swift patterns independent of any specific platform
- Wants complexity/size limits (SwiftLint thresholds) on agent-written code
Available Modules
concurrency-patterns/
Swift concurrency architecture and patterns.
- Swift 6.2 approachable concurrency features (incl.
nonisolated(nonsending), Apple's adoption doctrine)
- Structured concurrency (async let, TaskGroup, .task modifier, task-local values)
- Actors, isolation, reentrancy, @MainActor, Sendable
- Runtime internals + profiling (cooperative pool, unsafe primitives, Swift Concurrency Instrument)
- Continuations for bridging legacy APIs
- Swift 6 strict concurrency migration guide
concurrency/
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.
code-size/
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.
memory/
InlineArray, Span, and the Swift performance cost model.
- InlineArray: fixed-size, stack-allocated collections with zero heap overhead
- Span family: safe, non-escapable access to contiguous memory (+ OutputRawSpan, swift-binary-parsing)
- Lifetime dependencies and non-escapable type constraints
swift-performance.md: the cost model — allocation, ARC/retain-release, exclusivity checks, dispatch, generics vs existentials, closures, ~Copyable ownership
How to Use
- Identify user's need from their question
- Read relevant module files from subdirectories
- Apply the guidance to their specific context
- Cross-reference with platform-specific skills (ios/, macos/) as needed
1---2name: swift-development3description: Swift language patterns and best practices including concurrency, performance, and modern idioms. Use for Swift language-level code review or architecture guidance.4---5
6# Swift Development
7
8Swift language-level guidance that applies across all Apple platforms.
9
10## When This Skill Activates
11
12Use this skill when the user:
13- Asks about Swift concurrency (async/await, actors, Sendable, TaskGroup)
14- Needs help with Swift 6 strict concurrency migration
15- Has data race or actor isolation errors
16- Asks about **InlineArray**, **Span**, or low-level memory performance
17- Wants to eliminate heap allocations or replace unsafe pointers
18- Asks about modern Swift patterns independent of any specific platform
19- Wants complexity/size limits (SwiftLint thresholds) on agent-written code
20
21## Available Modules
22
23### concurrency-patterns/
24Swift concurrency architecture and patterns.
25- Swift 6.2 approachable concurrency features (incl. `nonisolated(nonsending)`, Apple's adoption doctrine)
26- Structured concurrency (async let, TaskGroup, .task modifier, task-local values)
27- Actors, isolation, reentrancy, @MainActor, Sendable
28- Runtime internals + profiling (cooperative pool, unsafe primitives, Swift Concurrency Instrument)
29- Continuations for bridging legacy APIs
30- Swift 6 strict concurrency migration guide
31
32### concurrency/
33Swift 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.
34
35### code-size/
36Complexity 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`.
37
38### memory/
39InlineArray, Span, and the Swift performance cost model.
40- InlineArray: fixed-size, stack-allocated collections with zero heap overhead
41- Span family: safe, non-escapable access to contiguous memory (+ OutputRawSpan, swift-binary-parsing)
42- Lifetime dependencies and non-escapable type constraints
43- `swift-performance.md`: the cost model — allocation, ARC/retain-release, exclusivity checks, dispatch, generics vs existentials, closures, `~Copyable` ownership
44
45## How to Use
46
471. Identify user's need from their question
482. Read relevant module files from subdirectories
493. Apply the guidance to their specific context
504. Cross-reference with platform-specific skills (ios/, macos/) as needed
rshankras