developing-ios-apps

iOS App Development

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

Critical Warnings

Issue	Cause	Solution
"Library not loaded: @rpath/Framework"	XcodeGen doesn't auto-embed SPM dynamic frameworks	Build in Xcode GUI first (not xcodebuild). See Troubleshooting
xcodegen generate loses signing	Overwrites project settings	Configure in project.yml target settings, not global
Command-line signing fails	Free Apple ID limitation	Use Xcode GUI or paid developer account ($99/yr)
"Cannot be set when automaticallyAdjustsVideoMirroring is YES"	Setting isVideoMirrored without disabling automatic	Set automaticallyAdjustsVideoMirroring = false first. See Camera
App signed as adhoc despite certificate	@electron/packager defaults continueOnError: true	Set continueOnError: false in osxSign. See Code Signing
"Cannot use password credentials, API key credentials..."	Passing teamId to @electron/notarize with API key auth	Remove teamId. notarytool infers team from API key. See Code Signing
EMFILE during signing (large embedded runtime)	@electron/osx-sign traverses all files in .app bundle	Add ignore filter + ulimit -n 65536 in CI. See Code Signing

Quick Reference

Task	Command
Generate project	xcodegen generate
Build simulator	xcodebuild -destination 'platform=iOS Simulator,name=iPhone 17' build
Build device (paid account)	xcodebuild -destination 'platform=iOS,name=DEVICE' -allowProvisioningUpdates build
Clean DerivedData	rm -rf ~/Library/Developer/Xcode/DerivedData/PROJECT-*
Find device name	xcrun xctrace list devices

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

iOS 17+ Only	iOS 16 Compatible
.onChange { old, new in }	.onChange { new in }
ContentUnavailableView	Custom VStack
AVAudioApplication	AVAudioSession
@Observable macro	@ObservableObject
SwiftData	CoreData/Realm

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

Error	Solution
"Library not loaded: @rpath/Framework"	SPM dynamic framework not embedded. Build in Xcode GUI first, then CLI works
"No Account for Team"	Add Apple ID in Xcode Settings → Accounts
"Provisioning profile not found"	Free account limitation. Use Xcode GUI or get paid account
Device not listed	Reconnect USB, trust computer on device, restart Xcode
DerivedData won't delete	Close Xcode first: pkill -9 Xcode && rm -rf ~/Library/Developer/Xcode/DerivedData/PROJECT-*

Free vs Paid Developer Account

Feature	Free Apple ID	Paid ($99/year)
Xcode GUI builds	✅	✅
Command-line builds	❌	✅
App validity	7 days	1 year
App Store	❌	✅
CI/CD	❌	✅

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

macOS Code Signing & Notarization

For distributing macOS apps (Electron or native) outside the App Store, signing + notarization is required. Without it users see "Apple cannot check this app for malicious software."

5-step checklist:

Step	What	Critical detail
1	Create CSR in Keychain Access	Common Name doesn't matter; choose "Saved to disk"
2	Request Developer ID Application cert at developer.apple.com	Choose G2 Sub-CA (not Previous Sub-CA)
3	Install .cer → must choose login keychain	iCloud/System → Error -25294 (private key mismatch)
4	Export P12 from login keychain with password	Base64: base64 -i cert.p12 | pbcopy
5	Create App Store Connect API Key (Developer role)	Downloa

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