iOS Resources
Hand-picked Articles

I built a sample app for this post called Tour Merch. It’s an App Clip plus a parent app, both written in Swift 6 with strict concurrency on. The clip lets you buy a shirt at a Metallica show with Apple Pay; the parent app lets you see every shirt you’ve bought across the tour. The whole companion repo is at the end of this post if you want to clone and poke.

What I want to walk through is the stuff that matters once you sit down to build one of these: what App Clips are actually for, how invocation works, how the project is wired, where Apple Pay forces your hand under Swift 6, and how the clip hands off to the parent app without losing the receipt.

Feature flags are a foundational tool for modern mobile development. They allow teams to control behavior at runtime, roll out features gradually, run experiments, and decouple deployment from release. In iOS applications, a well-designed feature flag system also becomes a central coordination mechanism between product, QA, and engineering.

This article walks through a type-safe and thread-safe feature flag implementation in Swift. It explains the design decisions behind the approach, the problems it solves, and how to integrate it into a real application.

SwiftUI provides built-in support for animations. In many cases, adding animations only requires attaching an animation to a state change.

There are two common ways to do this:

1. animation(_:value:) view modifier for animations when a certain state value changes
2. withAnimation(_:_:) global function which we can use to apply state changes and create animations for all views affected by them

In this article, we'll look at how both approaches work and when to use each of them.

Text recognition using Apple's Vision framework. The article compares the old API (VNRecognizeTextRequest with VNImageRequestHandler, synchronous perform, completion handlers) and the modern API introduced in iOS 18 and macOS 15 (RecognizeTextRequest, Swift native, Sendable, async/await). The modern version is cleaner: configure the request as a value type, call try await request.perform(on: image), get observations, extract top candidates. The article also covers recognition levels (.accurate vs .fast), language detection (automatic or manual), multi line documents, and the newer RecognizeDocumentsRequest for paragraphs instead of lines.

A deep dive into Apple's standardized component for empty, unavailable, or failed content states. Before iOS 17, every app built the same VStack with an icon, title, description, and button. ContentUnavailableView provides a canonical system component with platform consistent styling, accessibility defaults, and Dynamic Type support. The article covers basic usage with title and systemImage, the built in search variant (ContentUnavailableView.search), custom initializers with view builders for actions (like a retry button for network failures), real world production examples (failed requests, first time UX, empty invoices), accessibility considerations, state driven patterns with enum based loading states, common mistakes (overbuilding, generic messages, missing recovery actions, showing empty state during loading), and when not to use it (onboarding, paywalls, interactive tutorials).

Building an event bus for communication between loosely coupled parts of an app. The implementation focuses on type safety (events conform to a marker protocol), thread safety with NSLock, automatic cleanup when the subscriber is deallocated, explicit cancellation via SubscriptionToken, MainActor delivery for UI code, and AsyncStream support. The key design choice is that subscriptions follow the owner's lifetime (weak reference), not the token's. The bus cleans up dead subscriptions lazily during publish or subscribe operations. Publishing creates a snapshot of subscribers and delivers events synchronously outside the lock.

A detailed breakdown of five core SwiftUI gestures. TapGesture with count and coordinateSpace parameters. LongPressGesture with minimumDuration, onPressingChanged, and maximumDistance. DragGesture with .onChanged, .onEnded, and an advanced version using .updating with @GestureState, explaining value, state, and transaction parameters. MagnifyGesture with magnification and velocity. RotationGesture using two @State properties (currentAngle and finalAngle) to preserve rotation after the gesture ends. A separate section on gesture composition: .map for transforming data, .simultaneously for parallel execution (unwrapping optional .first and .second), and .sequenced for sequential gestures (switch statement on the enum).

A straight introduction to SwiftData, Apple's persistence framework for iOS 17. You will see how to define models with @Model, set up a model container, fetch data with @Query, insert and save via modelContext, filter with #Predicate, and link models with @Relationship. The code is minimal and clean.

A comparison of two parallel implementations of the same iOS feature. Team A used PRD driven AI TDD with test first development and an adversarial "convince me this is correct" review. Team B used a human in the loop iterative approach: write code, run it, hit edge cases, refactor. Expected A to be tighter and more correct. The opposite happened. B won on three of four dimensions. A was cleaner on architecture only. B had stronger tests (golden binary fixtures, integration invariants), better threading correctness (assert(!Thread.isMainThread)), production observability (logging, performance tracking), and documentation with rationale per decision. Five mechanisms explain the gap. TDD does not generate the highest leverage tests (golden fixtures require working code first). Spec plus test creates a closed loop where no one asks "what about interactions?" TDD is hostile to instrumentation because logs and tracking have no failing test. Adversarial review hardens claims but does not reframe scope. Micro commits make the refactor step invisible and easy to skip.

The article explains that @Environment(.scenePhase) works reliably only in a pure SwiftUI app with SwiftUI lifecycle. When a SwiftUI view is hosted inside UIKit via UIHostingController, scenePhase may not behave as expected because the view does not participate in SwiftUI's scene model. The recommended alternatives are observing UIApplication notifications (didBecomeActiveNotification, willResignActiveNotification) for app wide state, or UIScene notifications (didActivateNotification, willDeactivateNotification, didEnterBackgroundNotification, willEnterForegroundNotification) for scene level behavior closer to scenePhase semantics.