---

name: ios-dev description: iOS development skill for Swift, SwiftUI, Live Activities, WidgetKit, and XCTest. Use when implementing iOS features.

iOS Development Skill

Platform-specific knowledge for iOS development.

Tech Stack

Component	Technology
Language	Swift 5.9+
UI Framework	SwiftUI
Architecture	MVVM or TCA (follow project)
Testing	XCTest, XCUITest
Live Activities	ActivityKit
Widgets	WidgetKit

Coding Standards

Naming

• Variables/Functions: lowerCamelCase
• Types/Protocols: UpperCamelCase
• Constants: lowerCamelCase (not SCREAMING_CASE)
• Language: English

File Organization

// 1. Imports
import SwiftUI
import ActivityKit

// 2. Types (protocol, struct, class, enum)
struct ContentView: View {
    // 3. Properties (static, @State, let, var)
    // 4. Initializer
    // 5. Body / Methods
}

// 6. Extensions
extension ContentView {
    // ...
}

// 7. Previews
#Preview {
    ContentView()
}

SwiftUI Patterns

// Prefer small, composable views
struct FeatureView: View {
    @StateObject private var viewModel = FeatureViewModel()

    var body: some View {
        VStack {
            HeaderSection(title: viewModel.title)
            ContentSection(items: viewModel.items)
        }
        .task {
            await viewModel.load()
        }
    }
}

Comments

• Japanese OK for complex logic
• Avoid obvious comments
• Use // MARK: - for sections

Build Commands

# Build
xcodebuild -scheme <Scheme> -destination 'generic/platform=iOS' build

# Test
xcodebuild test \
  -scheme <Scheme> \
  -destination 'platform=iOS Simulator,name=iPhone 15'

# Clean
xcodebuild clean -scheme <Scheme>

Live Activities

Setup Checklist

• Add NSSupportsLiveActivities to Info.plist
• Create ActivityAttributes struct
• Create ActivityContent struct
• Implement start/update/end logic

Basic Pattern

struct MyActivityAttributes: ActivityAttributes {
    public struct ContentState: Codable, Hashable {
        var value: String
    }
    var name: String
}

// Start
let attributes = MyActivityAttributes(name: "Example")
let state = MyActivityAttributes.ContentState(value: "Initial")
let activity = try Activity.request(
    attributes: attributes,
    content: .init(state: state, staleDate: nil)
)

// Update
await activity.update(
    ActivityContent(state: newState, staleDate: nil)
)

// End
await activity.end(nil, dismissalPolicy: .immediate)

WidgetKit

Setup Checklist

• Add Widget Extension target
• Configure App Groups for data sharing
• Implement TimelineProvider
• Create Widget views

Data Sharing

// Write (main app)
let defaults = UserDefaults(suiteName: "group.com.example.app")
defaults?.set(value, forKey: "sharedKey")
WidgetCenter.shared.reloadAllTimelines()

// Read (widget)
let defaults = UserDefaults(suiteName: "group.com.example.app")
let value = defaults?.string(forKey: "sharedKey")

Testing

Unit Test Pattern

final class FeatureTests: XCTestCase {
    var sut: FeatureViewModel!

    override func setUp() {
        super.setUp()
        sut = FeatureViewModel()
    }

    override func tearDown() {
        sut = nil
        super.tearDown()
    }

    func test_initialState_isEmpty() {
        XCTAssertTrue(sut.items.isEmpty)
    }

    func test_load_populatesItems() async {
        await sut.load()
        XCTAssertFalse(sut.items.isEmpty)
    }
}

Common Issues

"Signing requires a development team"

• Open Xcode, select target, set Team in Signing & Capabilities

"No such module"

• Clean build folder: xcodebuild clean
• Check Swift Package dependencies

Widget not updating

• Call WidgetCenter.shared.reloadAllTimelines()
• Check App Groups configuration