iOS App Development

Build, configure, and deploy iOS applications using XcodeGen and Swift Package Manager.

Critical Warnings

Quick Reference

XcodeGen Configuration

Minimal project.yml

name: AppName
options:
  bundleIdPrefix: com.company
  deploymentTarget:
    iOS: "16.0"

settings:
  base:
    SWIFT_VERSION: "6.0"

packages:
  SomePackage:
    url: https://github.com/org/repo
    from: "1.0.0"

targets:
  AppName:
    type: application
    platform: iOS
    sources:
      - path: AppName
    settings:
      base:
        INFOPLIST_FILE: AppName/Info.plist
        PRODUCT_BUNDLE_IDENTIFIER: com.company.appname
        CODE_SIGN_STYLE: Automatic
        DEVELOPMENT_TEAM: TEAM_ID_HERE
    dependencies:
      - package: SomePackage

Code Signing Configuration

Personal (free) account: Works in Xcode GUI only. Command-line builds require paid account.

# In target settings
settings:
  base:
    CODE_SIGN_STYLE: Automatic
    DEVELOPMENT_TEAM: TEAM_ID  # Get from Xcode → Settings → Accounts

Get Team ID:

security find-identity -v -p codesigning | head -3

iOS Version Compatibility

API Changes by Version

Lowering Deployment Target

1. Update project.yml:

deploymentTarget:
  iOS: "16.0"

2. Fix incompatible APIs:

// iOS 17
.onChange(of: value) { oldValue, newValue in }
// iOS 16
.onChange(of: value) { newValue in }

// iOS 17
ContentUnavailableView("Title", systemImage: "icon")
// iOS 16
VStack {
    Image(systemName: "icon").font(.system(size: 48))
    Text("Title").font(.title2.bold())
}

// iOS 17
AVAudioApplication.shared.recordPermission
// iOS 16
AVAudioSession.sharedInstance().recordPermission

3. Regenerate: xcodegen generate

Device Deployment

First-time Setup

1. Connect device via USB
2. Trust computer on device
3. In Xcode: Settings → Accounts → Add Apple ID
4. Select device in scheme dropdown
5. Run (Cmd + R)
6. On device: Settings → General → VPN & Device Management → Trust

Command-line Build (requires paid account)

xcodebuild \
  -project App.xcodeproj \
  -scheme App \
  -destination 'platform=iOS,name=DeviceName' \
  -allowProvisioningUpdates \
  build

Common Issues

Free vs Paid Developer Account

SPM Dependencies

SPM Dynamic Framework Not Embedded

Root Cause: XcodeGen doesn't generate the "Embed Frameworks" build phase for SPM dynamic frameworks (like RealmSwift, Realm). The app builds successfully but crashes on launch with:

dyld: Library not loaded: @rpath/RealmSwift.framework/RealmSwift
  Referenced from: /var/containers/Bundle/Application/.../App.app/App
  Reason: image not found

Why This Happens:

• Static frameworks (most SPM packages) are linked into the binary - no embedding needed
• Dynamic frameworks (RealmSwift, etc.) must be copied into the app bundle
• XcodeGen generates link phase but NOT embed phase for SPM packages
• embed: true in project.yml causes build errors (XcodeGen limitation)

The Fix (Manual, one-time per project):

1. Open project in Xcode GUI
2. Select target → General → Frameworks, Libraries
3. Find the dynamic framework (RealmSwift)
4. Change "Do Not Embed" → "Embed & Sign"
5. Build and run from Xcode GUI first

After Manual Fix: Command-line builds (xcodebuild) will work because Xcode persists the embed setting in project.pbxproj.

Identifying Dynamic Frameworks:

# Check if a framework is dynamic
file ~/Library/Developer/Xcode/DerivedData/PROJECT-*/Build/Products/Debug-iphoneos/FRAMEWORK.framework/FRAMEWORK
# Dynamic: "Mach-O 64-bit dynamically linked shared library"
# Static: "current ar archive"

Adding Packages

packages:
  AudioKit:
    url: https://github.com/AudioKit/AudioKit
    from: "5.6.5"
  RealmSwift:
    url: https://github.com/realm/realm-swift
    from: "10.54.6"

targets:
  App:
    dependencies:
      - package: AudioKit
      - package: RealmSwift
        product: RealmSwift  # Explicit product name when package has multiple

Resolving Dependencies (China proxy)

git config --global http.proxy http://127.0.0.1:1082
git config --global https.proxy http://127.0.0.1:1082
xcodebuild -scmProvider system -resolvePackageDependencies

Never clear global SPM cache (~/Library/Caches/org.swift.swiftpm). Re-downloading is slow.

Camera / AVFoundation

Camera preview requires real device (simulator has no camera).

Quick Debugging Checklist

1. Permission: Added NSCameraUsageDescription to Info.plist?
2. Device: Running on real device, not simulator?
3. Session running: session.startRunning() called on background thread?
4. View size: UIViewRepresentable has non-zero bounds?
5. Video mirroring: Disabled automaticallyAdjustsVideoMirroring before setting isVideoMirrored?

Video Mirroring (Front Camera)

CRITICAL: Must disable automatic adjustment before setting manual mirroring:

// WRONG - crashes with "Cannot be set when automaticallyAdjustsVideoMirroring is YES"
connection.isVideoMirrored = true

// CORRECT - disable automatic first
connection.automaticallyAdjustsVideoMirroring = false
connection.isVideoMirrored = true

UIViewRepresentable Sizing Issue

UIViewRepresentable in ZStack may have zero bounds. Fix with explicit frame:

// BAD: UIViewRepresentable may get zero size in ZStack
ZStack {
    CameraPreviewView(session: session)  // May be invisible!
    OtherContent()
}

// GOOD: Explicit sizing
ZStack {
    GeometryReader { geo in
        CameraPreviewView(session: session)
            .frame(width: geo.size.width, height: geo.size.height)
    }
    .ignoresSafeArea()
    OtherContent()
}

Debug Logging Pattern

Add logging to trace camera flow:

import os
private let logger = Logger(subsystem: "com.app", category: "Camera")

func start() async {
    logger.info("start() called, isRunning=\(self.isRunning)")
    // ... setup code ...
    logger.info("session.startRunning() completed")
}

// For CGRect (doesn't conform to CustomStringConvertible)
logger.info("bounds=\(NSCoder.string(for: self.bounds))")

Filter in Console.app by subsystem.

For detailed camera implementation: See references/camera-avfoundation.md

Resources

• references/xcodegen-full.md - Complete project.yml options
• references/swiftui-compatibility.md - iOS version API differences
• references/camera-avfoundation.md - Camera preview debugging
• references/testing-mainactor.md - Testing @MainActor classes (state machines, regression tests)