Swift Language & Platform

You MUST use this skill for ANY Swift idiom review, ownership/noncopyable types, Transferable/drag-and-drop, debug deep links, or tvOS development.

Quick Reference

Symptom / Task	Reference
Outdated Swift patterns (Date(), CGFloat, DateFormatter)	See `skills/swift-modern.md`
Foundation modernization (FormatStyle, URL.documentsDirectory)	See `skills/swift-modern.md`
Common Claude hallucinations in Swift code	See `skills/swift-modern.md`
Noncopyable types (~Copyable)	See `skills/ownership-conventions.md`
borrowing/consuming parameter ownership	See `skills/ownership-conventions.md`
InlineArray, Span, value generics	See `skills/ownership-conventions.md`
Reducing ARC overhead	See `skills/ownership-conventions.md`
Drag and drop (.draggable, .dropDestination)	See `skills/transferable-ref.md`
Copy/paste (.copyable, PasteButton)	See `skills/transferable-ref.md`
ShareLink, content sharing	See `skills/transferable-ref.md`
Custom UTType declarations	See `skills/transferable-ref.md`
TransferRepresentation choices	See `skills/transferable-ref.md`
Debug-only deep links for simulator testing	See `skills/deep-link-debugging.md`
Navigate to specific screens for screenshots	See `skills/deep-link-debugging.md`
tvOS Focus Engine, Siri Remote input	See `skills/tvos.md`
tvOS storage constraints (no Documents dir)	See `skills/tvos.md`
tvOS text input, AVPlayer tuning	See `skills/tvos.md`
TVUIKit components	See `skills/tvos.md`

Decision Tree

dot

digraph swift {
    start [label="Swift task" shape=ellipse];
    what [label="What do you need?" shape=diamond];

    start -> what;
    what -> "skills/swift-modern.md" [label="modern idioms,\noutdated patterns,\nFoundation APIs"];
    what -> "skills/ownership-conventions.md" [label="~Copyable, borrowing,\nconsuming, InlineArray,\nSpan, ARC reduction"];
    what -> "skills/transferable-ref.md" [label="drag & drop, copy/paste,\nShareLink, UTTypes,\nTransferable conformance"];
    what -> "skills/deep-link-debugging.md" [label="debug deep links,\nsimulator navigation,\nscreenshot automation"];
    what -> "skills/tvos.md" [label="tvOS app,\nFocus Engine,\nSiri Remote, storage"];
}

Outdated Swift patterns / modern API replacements / Claude hallucinations? ->
```
skills/swift-modern.md
```
~Copyable / borrowing / consuming / InlineArray / Span? ->
```
skills/ownership-conventions.md
```
Drag and drop / copy/paste / ShareLink / Transferable / UTTypes? ->
```
skills/transferable-ref.md
```
Debug deep links / simulator navigation / screenshot automation? ->
```
skills/deep-link-debugging.md
```
tvOS development / Focus Engine / Siri Remote / storage / AVPlayer? ->
```
skills/tvos.md
```
Swift concurrency (async/await, actors, Sendable) ->
```
/skill axiom-concurrency
```
Swift performance (COW, ARC, generics optimization) -> See axiom-performance (skills/swift-performance.md)
Codable patterns (JSON, CodingKeys, enum serialization) -> See axiom-data (skills/codable.md)

Conflict Resolution

swift vs concurrency: When Swift 6 concurrency errors appear:

Use concurrency, NOT swift -- Concurrency errors are actor isolation / Sendable issues.
```
skills/swift-modern.md
```
covers concurrency posture (defaults), but detailed patterns live in axiom-concurrency.

swift vs performance: When optimizing Swift code:

Use swift for ownership if the question is borrowing/consuming/~Copyable/InlineArray/Span ->
```
skills/ownership-conventions.md
```
Use performance if the question is COW, ARC profiling, generic specialization, or Instruments workflows -> axiom-performance

swift vs swiftui: When implementing drag and drop or copy/paste:

Use swift for Transferable conformance, representation choices, UTType declarations ->
```
skills/transferable-ref.md
```
Use swiftui for view-level modifiers (.draggable, .dropDestination styling, animations)

swift vs integration: When sharing content:

ShareLink + Transferable -> use swift (
```
skills/transferable-ref.md
```
)
UIActivityViewController customization, share extensions -> use integration

swift vs axiom-build: When tvOS build fails:

Environment/Xcode issues -> use axiom-build first
tvOS platform-specific code issues (Focus Engine, storage, no WebView) -> use swift (
```
skills/tvos.md
```
)

Critical Patterns

Modern Swift Idioms (

skills/swift-modern.md

12+ outdated patterns Claude defaults to (Date(), CGFloat, DateFormatter, DispatchQueue.main.async)
Foundation modernization (FormatStyle, URL.documentsDirectory, .replacing())
SwiftUI convenience APIs Claude misses (ContentUnavailableView.search, LabeledContent)
Swift 6.3 concurrency posture defaults
9 common Claude hallucinations with corrections

Ownership & Noncopyable Types (

skills/ownership-conventions.md

borrowing/consuming parameter modifiers with 7 patterns
~Copyable types: FileHandle pattern, limitations table, common compiler errors
InlineArray: fixed-size stack-allocated arrays with value generics
Span family: safe contiguous memory access replacing UnsafeBufferPointer
Decision tree for when ownership modifiers help vs when to skip

Transferable & Sharing (

skills/transferable-ref.md

Decision tree: CodableRepresentation vs DataRepresentation vs FileRepresentation vs ProxyRepresentation
Drag and drop, copy/paste, ShareLink with complete SwiftUI API
Custom UTType declarations (Swift + Info.plist, both required)
7 common errors with fixes (representation ordering, missing Info.plist, hit testing)
UIKit bridging via NSItemProvider

Debug Deep Links (

skills/deep-link-debugging.md

Debug-only URL scheme for simulator navigation
NavigationPath integration for robust routing
State configuration links (error states, empty states)
Integration with /axiom:screenshot and simulator-tester agent
60-75% faster iteration with visual verification

tvOS Development (

skills/tvos.md

Dual focus system (UIKit Focus Engine + SwiftUI @FocusState)
Siri Remote input (two generations, three input layers)
Storage constraints (no Documents directory, iCloud required)
No WebView (JavaScriptCore only, no DOM)
AVPlayer tuning, Menu button state machine
TVUIKit components

Anti-Rationalization

Thought	Reality
"Date() is fine, everyone uses it"	`Date.now` has been the modern pattern since Swift 5.6. `skills/swift-modern.md` lists 12+ patterns Claude gets wrong.
"I don't need ownership modifiers"	For most code, correct. But ~Copyable types require them, and large value types in hot paths benefit measurably.
"Transferable is just Codable for drag and drop"	Transferable has 4 representation types, ordering rules, and Info.plist requirements. Getting it wrong causes silent cross-app failures.
"I'll just use the same code as iOS for tvOS"	tvOS has no Documents directory, no WebView, a dual focus system, and two generations of remote hardware. It compiles fine and fails at runtime.
"Debug deep links are overkill"	Manual navigation costs 2-3 minutes per iteration. Deep links cut it to 45 seconds. Over a debugging session, that's hours saved.
"CGFloat is what SwiftUI uses"	Swift 5.5+ has implicit Double-CGFloat bridging. Use Double everywhere except optionals, inout, and ObjC-bridged APIs.
"I'll add the Info.plist entry later"	Custom UTTypes work in-app without Info.plist but silently fail cross-app. This is the #1 "works in dev, fails in prod" Transferable issue.
"FormatStyle is too verbose"	`val.formatted(.number.precision(.fractionLength(2)))` is type-safe and localized. `String(format:)` is neither.

Example Invocations

User: "Is this Swift code using modern patterns?" -> Read:

skills/swift-modern.md

User: "How do I use borrowing and consuming?" -> Read:

skills/ownership-conventions.md

User: "How do I make my model draggable?" -> Read:

skills/transferable-ref.md

User: "How do I implement ShareLink with a custom preview?" -> Read:

skills/transferable-ref.md

User: "I need debug deep links for simulator testing" -> Read:

skills/deep-link-debugging.md

User: "I'm building a tvOS app and focus navigation doesn't work" -> Read:

skills/tvos.md

User: "What is InlineArray and when should I use it?" -> Read:

skills/ownership-conventions.md

User: "My drag and drop works in-app but not across apps" -> Read:

skills/transferable-ref.md

User: "tvOS keeps losing my saved data" -> Read:

skills/tvos.md

User: "How do I optimize large struct passing?" -> Read:

skills/ownership-conventions.md

User: "I need to fix my async/await code" -> See

/skill axiom-concurrency

User: "Check my code for Swift 6 concurrency issues" -> See

/skill axiom-concurrency

axiom-swift

NPX Install

Tags

SKILL.md Content