iOS Development

Start here. This skill coordinates the Apple skills collection — it tells you which skill to use and when, so you get opinionated guidance and full API references together.

Operating Rules

• SwiftUI and UIKit are both first-class — pick whichever fits the task. UIKit is a valid choice whenever it gives more control or flexibility; when bridging the two, watch state sync, lifecycle, and animation/environment boundaries.
• Do not enforce specific architectures (MVVM, VIPER, MV, TCA, etc.) — encourage separating business logic from views without mandating how
• Hold a high bar for UI craft: apps should feel current-generation — fluid, design-forward, alive. Sweat the tiny details. Custom components, novel interactions, and custom Metal shaders are all in-bounds when they serve the experience; system defaults are a floor, not a ceiling.
• Do not prescribe how that craft is delivered — no house style, no "Apple-approved" gatekeeping, no aesthetic checklists. Design direction is your own judgment call, made per app. The hig and ios-liquid-glass skills document what the system provides; they are references, not style mandates. When the task is designing a screen or making it look good, there is no doc to route to — design from your own taste; grep references only when you need API mechanics or a factual minimum (e.g. hit-target sizes).
• Present performance optimizations as suggestions backed by reasoning, not blanket requirements
• When you need exact API details, grep the framework reference skills — they contain full Apple documentation

Task Workflows

Review existing code

1. Read the code and identify which topics apply
2. Run the Correctness Checklist below — violations are bugs
3. Use the Topic Router to load the relevant guide for each topic
4. For API correctness, grep the matching framework reference skill

Improve existing code

1. Run the correctness checklist first
2. For performance issues: use guide-swiftui-performance-audit
3. For navigation, state, or pattern questions: use Apple's swiftui-specialist (shipped with Xcode 27; exported to the user skills dir), then the swiftui API reference
4. For API details: grep the matching framework reference skill

Build a new feature

1. Design data flow first — identify owned vs. injected state
2. For UI patterns and app wiring: use Apple's swiftui-specialist, then the swiftui API reference
3. For API details: grep the matching framework reference skill
4. Structure views for optimal diffing — extract subviews early
5. Run the correctness checklist before finishing

Topic Router

The Guide column has opinionated, short pattern guides. The API Reference column has full Apple documentation as grepable Markdown — use apple-docs-index to find which framework has what.

Topic	Guide	API Reference
State management	swiftui-specialist (Apple, Xcode 27)	swiftui (state.md, binding.md, observation.md, environment.md)
View composition	—	swiftui (view-protocol.md)
Performance	guide-swiftui-performance-audit	—
Navigation	swiftui-specialist (Apple, Xcode 27)	swiftui (navigationstack.md, navigationsplitview.md, navigationlink.md)
Sheets & modals	swiftui-specialist (Apple, Xcode 27)	swiftui (sheet.md, inspector.md, alert.md, confirmationdialog.md)
Lists & ForEach	swiftui-specialist (Apple, Xcode 27)	swiftui (list.md)
ScrollView	swiftui-specialist (Apple, Xcode 27)	swiftui (scrollview.md)
Forms & input	—	swiftui (form.md, textfield.md, picker.md, toggle.md, slider.md)
Charts	guide-swiftui-charts	swiftui (chart.md, charts-overview.md)
Animations	swiftui-specialist (Apple, Xcode 27)	swiftui (swiftui-overview.md)
Layout	swiftui-specialist (Apple, Xcode 27)	swiftui (geometryreader.md, grid.md, hstack.md, vstack.md, zstack.md, spacer.md)
TabView	swiftui-specialist (Apple, Xcode 27)	swiftui (tabview.md)
Liquid Glass	—	ios-liquid-glass
Accessibility	swiftui-specialist (Apple, Xcode 27)	hig (a11y/ergonomic facts)
macOS apps	guide-macos-spm-packaging	swiftui, uikit
Data persistence	guide-swiftdata	swiftdata
Testing	guide-swift-testing	swift-testing, xcuitest
Concurrency	guide-swift-concurrency	swift-concurrency
In-app purchases	—	storekit
Maps	—	mapkit
Health data	—	healthkit
Notifications	—	usernotifications
App Intents / Siri	app-intents-specialist, app-intents-whats-new-27 (Apple, Xcode 27)	—
Widgets	—	widgetkit
App Store metadata	apple-aso	—
Finding docs	apple-docs-index	—

Correctness Checklist

These are hard rules — violations are always bugs:

• @State properties are private
• @Binding only where a child needs to mutate parent state
• Values passed in are never declared as @State — they silently ignore updates
• Use @State with @Observable classes — not @StateObject or ObservableObject
• Use @Bindable for injected observables that need bindings
• ForEach uses stable identity — never .indices on dynamic content
• Each ForEach element produces a constant number of views
• .animation(_:value:) always includes the value: parameter
• @FocusState properties are private
• @Observable classes are @MainActor — Swift 6 strict concurrency requires it
• Property wrappers (@AppStorage, @SceneStorage, @Query) inside @Observable classes are marked @ObservationIgnored — they conflict with the macro and cause compiler errors
• No business logic in body — use .task, .onChange, or methods
• No AnyView unless truly unavoidable — fix with better composition

Related Skills

System API reference:

• /ios-liquid-glass — Liquid Glass API reference

Workflow guides:

• /swiftui-specialist — Apple's SwiftUI best practices (Xcode 27): structure, data flow, environment, ForEach identity, localization, soft deprecations
• /swiftui-whats-new-27 — iOS 27 SwiftUI changes (@State macro, @ContentBuilder, reorderable, toolbar overflow)
• /guide-swiftui-charts — Marks, axes, selection, styling, accessibility
• /guide-swiftui-performance-audit — Diagnose and fix performance issues
• /guide-swift-testing — Swift Testing patterns, async tests, common agent mistakes
• /guide-swift-concurrency — Concurrency patterns, actors, diagnostics, bug patterns
• /guide-swiftdata — SwiftData patterns, predicates, CloudKit constraints
• /guide-macos-spm-packaging — Build macOS apps with SwiftPM

Utilities:

• /apple-docs-index — Find the right Apple documentation
• /apple-aso — App Store Optimization