# Mobile IOS Native > Native iOS development with Swift, SwiftUI, and the modern Apple platforms stack (iOS 16+). Use when building, reviewing, or refactoring iOS apps using SwiftUI, Swift Concurrency (async/await, actors), Observation, SwiftData/Core Data, Combine, and Xcode tooling. Use when this capability is needed. - Skill: `tomevault-io/mobile-ios-native` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/mobile-ios-native` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/mobile-ios-native/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/mobile-ios-native --- # Mobile iOS Native Modern, production-grade iOS engineering with Swift and SwiftUI on Apple platforms. ## When to Use - Building or reviewing native iOS apps (Swift + SwiftUI) - Migrating from UIKit to SwiftUI, or Combine to Swift Concurrency - Designing iOS-specific architecture (scenes, lifecycle, background modes) - Integrating Apple platform APIs (HealthKit, CoreLocation, AVFoundation, WidgetKit, App Intents) - Reviewing Xcode build settings, code signing, App Store Connect, or TestFlight workflows ## Toolchain Defaults - Language: Swift 5.10+ (Swift 6 mode where dependencies allow), strict concurrency checking on - UI: SwiftUI first; UIKit only where SwiftUI gaps exist (use `UIViewRepresentable` bridges) - Min iOS: 16 (lower only with explicit reason); use availability checks for newer APIs - Build: Xcode latest stable, Swift Package Manager (SPM) preferred over CocoaPods/Carthage - State: `@Observable` (Observation framework, iOS 17+), `@State`, `@Binding`, `@Environment`; Combine only for legacy bridges - Persistence: SwiftData (iOS 17+) or Core Data with NSPersistentCloudKitContainer; Keychain for secrets - Networking: `URLSession` with `async/await`; `Codable` + JSON; `Sendable` models - Background: BGTaskScheduler, background URLSession, push-triggered fetch - Testing: XCTest, Swift Testing (when stable), XCUITest, snapshot tests via SwiftSnapshotTesting ## Architecture Rules 1. Prefer SwiftUI views composed of small, focused subviews; pass state via `@Binding` and environment. 2. Use `@Observable` model classes (or `ObservableObject` pre-iOS 17) as the source of truth; views are derived. 3. Layer the app: `Features` (views + view models) → `Domain` (pure Swift) → `Data` (repositories, services). Keep Domain free of UIKit/SwiftUI imports. 4. Inject dependencies through initializers or `Environment`; avoid singletons except for system-bridged services. 5. Use Swift Concurrency end-to-end: `async`/`await`, `Task`, `TaskGroup`, `AsyncSequence`. Isolate mutable shared state with `actor`s. 6. Mark types `Sendable` where they cross concurrency domains; turn on strict concurrency checking and resolve all warnings. 7. Use `@MainActor` for UI-touching code; never block the main thread with synchronous I/O. ## SwiftUI Rules - Keep view bodies small; extract subviews to enable better diffing and previews. - Use `Identifiable` models with stable IDs in `ForEach`; avoid index-based identity. - Prefer `LazyVStack`/`LazyHStack`/`List` for large collections; use `.id()` and `.task(id:)` carefully. - Use `.task { }` for async work tied to view lifetime; cancel propagates automatically. - Animate with `withAnimation` and `matchedGeometryEffect`; respect Reduce Motion. - Theming: support Dynamic Type, Dark Mode, high-contrast, and SF Symbols variants. - Accessibility: every actionable element has a label; group related elements; provide rotor/custom actions where appropriate. ## Concurrency & Data - Use `async let`, `TaskGroup`, and `AsyncStream` instead of `DispatchQueue` callbacks. - Cancellation is cooperative — check `Task.checkCancellation()` in long loops. - Repositories return `async throws` functions or `AsyncSequence`; map errors to a domain `Error` enum. - SwiftData: model context is main-actor isolated; use background contexts for heavy writes. - Core Data: use `NSPersistentContainer.newBackgroundContext()` and merge changes; never pass `NSManagedObject` across contexts. - Networking: configure `URLSessionConfiguration` (timeouts, waitsForConnectivity), pin certificates for sensitive endpoints. ## Performance - Profile with Instruments (Time Profiler, Allocations, Hangs, SwiftUI, Animation Hitches) before optimizing. - Cold launch budget: < 400ms to first useful frame on iPhone 12 / mid-range device. - Avoid `@StateObject`/`@Observable` churn; pass minimal state down the tree. - Use `drawingGroup()` for complex composited views; avoid offscreen passes when not needed. - Image pipeline: load correctly sized images, prefer `Image(uiImage:)` from a cached `UIImage`, decode off-main when needed. - Reduce app size: enable bitcode-free distribution, App Thinning, on-demand resources for large assets. - Watch hangs and disk writes via MetricKit; ship `MXMetricManager` integration in production. ## Security - Store secrets in Keychain with `kSecAttrAccessibleAfterFirstUnlockThisDeviceOnly` minimum. - Use App Transport Security (ATS) with no exceptions; pin certificates for sensitive endpoints. - Enable Hardened Runtime, App Sandbox, and Data Protection (`NSFileProtectionComplete` where possible). - Use `LAContext` for biometric gating; require recent authentication for sensitive actions. - Validate all Universal Links / deep link inputs; reject unexpected schemes. - Privacy: declare required reason APIs, fill out the Privacy Manifest (`PrivacyInfo.xcprivacy`), and minimize tracked data. ## Testing - Unit-test domain code with no UI dependencies; use protocol-based fakes injected via initializers. - Use Swift Testing or XCTest with `async` tests; avoid expectations for async code. - Snapshot-test critical SwiftUI screens across Dynamic Type sizes and color schemes. - XCUITest for end-to-end smoke flows; keep them short and deterministic. - Run tests on multiple device classes (small phone, large phone, iPad) in CI. ## Release & Distribution - Use Xcode Cloud or Fastlane for automated builds, signing, and TestFlight uploads. - Manage signing with App Store Connect API keys; never commit `.p12` or provisioning profiles. - Use phased release on the App Store; monitor crash-free users and MetricKit signals. - Maintain a Privacy Manifest, App Privacy details, and accurate export compliance. - Use TestFlight internal/external groups for staged validation before submission. ## Anti-Patterns - Force-unwrapping (`!`) outside tests or unmistakably safe boundaries - Using `DispatchQueue.main.async` from inside `async` code instead of `@MainActor` - Long-lived `Task { }` without storing/cancelling; leaking work after view dismissal - `ObservableObject` with many `@Published` properties causing whole-view invalidation - Storing `UIViewController` or `UIView` references in models - Hard-coding strings for accessibility labels in non-localized form - Shipping without `Sendable`/strict concurrency warnings resolved - Disabling ATS or skipping Privacy Manifest entries ## Review Checklist - [ ] Min iOS, Swift, and Xcode versions are current and aligned - [ ] SwiftUI views are small, hoist state, and use stable identities - [ ] Concurrency: `async/await`, `actor` isolation, `Sendable` correctness, `@MainActor` on UI - [ ] Domain layer is UI-framework free; dependencies injected via init/environment - [ ] Persistence uses SwiftData/Core Data correctly across contexts - [ ] Secrets in Keychain; ATS on; Privacy Manifest filled out - [ ] Accessibility: Dynamic Type, VoiceOver labels, Reduce Motion respected - [ ] Crash, hang, and launch metrics are monitored (MetricKit + Crashlytics/Sentry) --- > Source: [SwapnilPopat/ai-assistant-skills](https://github.com/SwapnilPopat/ai-assistant-skills) — distributed by [TomeVault](https://tomevault.io).