Glossary

iOS and Apple development has a lot of terms that don't have direct equivalents in web development. This glossary covers the ones you'll encounter throughout this series.

@MainActor

A Swift concurrency annotation that ensures code runs on the main thread. All UI work in SwiftUI must be on the main thread. Apply to your view models: @MainActor @Observable class HomeViewModel.

@Observable

The modern (iOS 17+) way to create observable objects in Swift. Replaces ObservableObject and @Published. Much simpler: just annotate the class with @Observable and any var property automatically triggers UI updates when it changes.

APNs

Apple Push Notification service. Apple's system for delivering push notifications to iOS devices. Your server sends notifications to APNs, which delivers them to the device.

Archive

A compiled, release-ready build of your app. Required before uploading to TestFlight or the App Store. Created via Xcode's Product → Archive menu.

Asset Catalog

Assets.xcassets — the file where you store images, colours, app icons, and other assets. Colours defined here can be referenced in SwiftUI as Color("BrandPrimary") and automatically support dark mode variants.

Bundle ID

A unique identifier for your app in reverse-domain format: com.yourname.appname. Ties your app to your Apple Developer account. Hard to change once submitted to the App Store.

DerivedData

Xcode's build cache, located at ~/Library/Developer/Xcode/DerivedData. When Xcode behaves unexpectedly, deleting this folder and rebuilding fixes most issues.

Entitlements

Permissions your app needs from the system, declared in a .entitlements file. Examples: push notifications, iCloud, Sign in with Apple. Xcode manages these via the Signing & Capabilities tab.

HIG

Human Interface Guidelines. Apple's comprehensive design documentation covering how iOS apps should look and behave. Violating HIG principles can result in App Store rejection. Required reading: developer.apple.com/design/human-interface-guidelines

Info.plist

A configuration file that declares your app's capabilities, permissions, and metadata to iOS. Every permission your app requests (camera, location, etc.) needs a corresponding description key here explaining why you need it.

Liquid Glass

Apple's design language introduced in iOS 26 (2025). Creates translucent, blurred surfaces using the .glassEffect() SwiftUI modifier. Always gate behind #available(iOS 26, *) with a material-based fallback.

NavigationStack

The modern (iOS 16+) navigation container in SwiftUI. Replaces the deprecated NavigationView. Supports programmatic navigation via a path binding.

Provisioning Profile

A file that ties your app's Bundle ID, signing certificate, and (for development) specific devices together. Xcode manages these automatically with "Automatically manage signing" enabled.

SF Symbols

Apple's system icon library with 5,000+ icons that automatically scale, adapt to Dynamic Type, and support dark mode. Use in SwiftUI: Image(systemName: "star.fill"). Browse at developer.apple.com/sf-symbols.

Simulator

A software simulation of iPhone and iPad that runs on your Mac, included with Xcode. Faster than physical device testing for most development. Some hardware features (push notifications, camera, haptics) require a real device.

SwiftData

Apple's modern (iOS 17+) persistence framework. Replaces Core Data with a Swift-native API. Define models with @Model class annotation, query with @Query.

TestFlight

Apple's beta testing platform, built into App Store Connect. Distribute builds to up to 100 internal testers (no review) or 10,000 external testers (brief review). The standard staging environment before App Store release.

Xcode

Apple's IDE for building apps on all Apple platforms. Required for building iOS apps — there's no alternative. Download from the Mac App Store. Includes Simulator, Instruments, and all debugging tools.

Xcode Previews

Real-time SwiftUI rendering in Xcode's Canvas. Defined with #Preview {} at the bottom of a view file. Renders instantly on save without rebuilding the app — your primary UI development loop.