iOS Basics Skill

Foundation knowledge for iOS application development including project setup, app lifecycle, and configuration.

Prerequisites

• Xcode 15+ installed
• Apple Developer account (for device testing)
• macOS Sonoma or later recommended

Parameters

parameters:
  ios_deployment_target:
    type: string
    default: "15.0"
    description: Minimum iOS version supported
  device_family:
    type: array
    items: [iphone, ipad]
    default: [iphone, ipad]
  interface_style:
    type: string
    enum: [storyboard, programmatic, swiftui]
    default: programmatic

Topics Covered

App Lifecycle

State	Description	Callback
Not Running	App not launched	-
Inactive	Transitioning	sceneWillResignActive
Active	Running in foreground	sceneDidBecomeActive
Background	Running in background	sceneDidEnterBackground
Suspended	In memory, not executing	-

Project Structure

MyApp/
├── MyApp.xcodeproj
├── MyApp/
│   ├── App/
│   │   ├── AppDelegate.swift
│   │   ├── SceneDelegate.swift
│   │   └── Info.plist
│   ├── Features/
│   │   └── Home/
│   │       ├── HomeViewController.swift
│   │       └── HomeViewModel.swift
│   ├── Core/
│   │   ├── Extensions/
│   │   ├── Utilities/
│   │   └── Services/
│   └── Resources/
│       ├── Assets.xcassets
│       └── LaunchScreen.storyboard
└── MyAppTests/

Info.plist Keys

Key	Purpose	Required
CFBundleDisplayName	App name shown to user	Yes
CFBundleIdentifier	Unique app identifier	Yes
UILaunchStoryboardName	Launch screen	Yes
NSCameraUsageDescription	Camera permission	If using camera
NSPhotoLibraryUsageDescription	Photo library permission	If accessing photos
UIBackgroundModes	Background capabilities	If running in background

Code Examples

SceneDelegate Setup (iOS 13+)

class SceneDelegate: UIResponder, UIWindowSceneDelegate {
    var window: UIWindow?
    private var appCoordinator: AppCoordinator?

    func scene(_ scene: UIScene,
               willConnectTo session: UISceneSession,
               options connectionOptions: UIScene.ConnectionOptions) {

        guard let windowScene = scene as? UIWindowScene else { return }

        let window = UIWindow(windowScene: windowScene)
        let navigationController = UINavigationController()

        appCoordinator = AppCoordinator(navigationController: navigationController)
        appCoordinator?.start()

        window.rootViewController = navigationController
        window.makeKeyAndVisible()
        self.window = window
    }

    func sceneDidEnterBackground(_ scene: UIScene) {
        // Save state, release resources
        CoreDataStack.shared.saveContext()
    }

    func sceneWillEnterForeground(_ scene: UIScene) {
        // Refresh data if needed
        NotificationCenter.default.post(name: .appWillEnterForeground, object: nil)
    }
}

Permission Request Pattern

import AVFoundation
import Photos

final class PermissionManager {
    static let shared = PermissionManager()

    func requestCameraPermission() async -> Bool {
        switch AVCaptureDevice.authorizationStatus(for: .video) {
        case .authorized:
            return true
        case .notDetermined:
            return await AVCaptureDevice.requestAccess(for: .video)
        case .denied, .restricted:
            return false
        @unknown default:
            return false
        }
    }

    func requestPhotoLibraryPermission() async -> Bool {
        let status = PHPhotoLibrary.authorizationStatus(for: .readWrite)

        switch status {
        case .authorized, .limited:
            return true
        case .notDetermined:
            let newStatus = await PHPhotoLibrary.requestAuthorization(for: .readWrite)
            return newStatus == .authorized || newStatus == .limited
        case .denied, .restricted:
            return false
        @unknown default:
            return false
        }
    }

    func openSettings() {
        guard let url = URL(string: UIApplication.openSettingsURLString) else { return }
        UIApplication.shared.open(url)
    }
}

Background Task Handling

import BackgroundTasks

final class BackgroundTaskManager {
    static let shared = BackgroundTaskManager()

    private let refreshTaskId = "com.app.refresh"
    private let processingTaskId = "com.app.processing"

    func registerTasks() {
        BGTaskScheduler.shared.register(forTaskWithIdentifier: refreshTaskId, using: nil) { task in
            self.handleAppRefresh(task: task as! BGAppRefreshTask)
        }

        BGTaskScheduler.shared.register(forTaskWithIdentifier: processingTaskId, using: nil) { task in
            self.handleProcessing(task: task as! BGProcessingTask)
        }
    }

    func scheduleRefresh() {
        let request = BGAppRefreshTaskRequest(identifier: refreshTaskId)
        request.earliestBeginDate = Date(timeIntervalSinceNow: 15 * 60) // 15 min

        do {
            try BGTaskScheduler.shared.submit(request)
        } catch {
            Logger.background.error("Failed to schedule refresh: \(error)")
        }
    }

    private func handleAppRefresh(task: BGAppRefreshTask) {
        scheduleRefresh() // Reschedule

        let refreshTask = Task {
            do {
                try await DataSyncService.shared.syncAll()
                task.setTaskCompleted(success: true)
            } catch {
                task.setTaskCompleted(success: false)
            }
        }

        task.expirationHandler = {
            refreshTask.cancel()
        }
    }
}

Troubleshooting

Common Issues

Issue	Cause	Solution
Black screen on launch	Missing root VC	Set window.rootViewController
Permission dialog not showing	Already denied	Check status, guide to Settings
Background task not running	Not registered	Call register in didFinishLaunching
Launch image wrong size	Missing assets	Add all required sizes to LaunchScreen

Debug Tips

# Simulate background fetch
xcrun simctl spawn booted debug-background refresh com.app.bundleid

# Check app lifecycle in console
# Filter: subsystem:com.apple.UIKit category:Lifecycle

# Reset permissions
xcrun simctl privacy booted reset all com.app.bundleid

Validation Rules

validation:
  - rule: info_plist_usage_descriptions
    severity: error
    check: All permission usage descriptions must be non-empty
  - rule: launch_screen_required
    severity: error
    check: LaunchScreen.storyboard or launch screen in Info.plist
  - rule: supported_orientations
    severity: warning
    check: Define supported orientations for all device types

Integration Patterns

// AppDelegate + SceneDelegate coordination
extension Notification.Name {
    static let appWillEnterForeground = Notification.Name("appWillEnterForeground")
    static let appDidBecomeActive = Notification.Name("appDidBecomeActive")
    static let userDidLogin = Notification.Name("userDidLogin")
}

Usage

Skill("swift-ios-basics")

Related Skills

• swift-uikit - UIKit components
• swift-swiftui - SwiftUI alternative
• swift-testing - Testing iOS apps