Those Who Swift - Issue 280
Weekly note ✏️This week’s articles share a common thread: frameworks can change significantly beneath APIs that look exactly the same. SwiftUI’s compiler performance is improving, Have you ever had to investigate a SwiftUI or UIKit behavior that the documentation couldn’t explain? Hit reply—I’d love to hear what you found.
Under SwiftUI's Hood, Nothing Is As Simple As It Lookswith Divya Ravi — Technical Editor, iOS engineer Seven years after its introduction, SwiftUI still asks developers to trust a considerable amount of hidden machinery. This week’s reading made a strong case for looking beneath that abstraction. Start with By relying on That distinction matters. When build performance improves without an obvious source change, it is easy to treat it as compiler magic. Understanding the implementation gives us something more useful: a clearer mental model for why certain view structures are expensive and why newer APIs may compile faster. A similar change is happening with Stewart Lynch found that in Xcode 27, Previously, the initializer expression could be evaluated during every view recreation, even when SwiftUI ultimately preserved the existing state value. With the macro implementation, that expression is evaluated lazily. For a simple integer or Boolean, the difference is unlikely to matter. For state initialized through a database lookup, file operation, or expensive computation, it can eliminate work that developers may not have realized was happening. These two changes approach the same problem from different directions. That brings us to Yakov Manshin’s “SwiftUI After 7 Years: A Story of Mediocrity,” a deliberately sharp retrospective that generated more than 300 comments on Hacker News. His central argument is difficult to dismiss completely: after seven years, “it is still a young framework” becomes a less convincing explanation for persistent problems. Focus management, drag-and-drop, platform inconsistencies, and difficult edge cases have survived several release cycles. I do not agree with every conclusion in the article, but the larger tension is real. SwiftUI’s internals continue to improve, while some visible limitations remain stubbornly familiar. Those are separate measures of maturity. Compiler performance can improve dramatically while developers still struggle with basic interactions. A framework can gain powerful new APIs without resolving gaps in older ones. When we say SwiftUI has come a long way, it is worth being precise about which part of SwiftUI we mean. Chang-Jui Lin’s article on building an EPUB reader with CoreText offers a practical counterpoint. Instead of adapting a WebView or relying on a higher-level text component, Lin built directly on CoreText to support reflowable content, fixed layouts, media overlays, and bidirectional text. It is a much lower level of abstraction—and a much larger engineering commitment. But it also provides the control required for a problem that higher-level frameworks do not solve cleanly. That is not an argument for rebuilding every framework primitive. Most abstractions are valuable precisely because they prevent us from owning that complexity. But when an abstraction becomes the constraint, understanding the layer below it can reveal options that are otherwise easy to miss. The broader lesson from this week is not that SwiftUI is good or bad. It is that no framework should remain a complete black box. The engineers who diagnose difficult problems fastest are often the ones willing to inspect the generated code, profile the rebuild, trace the macro expansion, or move down the stack when the current abstraction stops being useful. Frameworks will continue to improve while retaining frustrating gaps—sometimes within the same release. The durable skill is learning how to investigate what the framework is actually doing. That understanding makes debugging faster, design decisions clearer, and point-release surprises far less surprising. What is the last SwiftUI, UIKit, or Swift behavior you had to reverse-engineer because the documentation did not explain enough? Related reading on this week's theme 📚ContentBuilder Explained: The Secret Behind SwiftUI's Type-Checking SpeedupAn investigation into how Apple improved SwiftUI type-checking performance through 📍Level: Advanced A Change of StateA focused demonstration of 📍Level: Intermediate SwiftUI After 7 Years: A Story of MediocrityA critical assessment of SwiftUI’s maturity and the framework limitations that remain after seven years. You may not agree with every argument, but it is a useful prompt to reconsider which rough edges we have started treating as normal. 📍Level: Advanced Adapting EPUB 3 Features to CoreText in Yuedu ReaderA detailed look at implementing EPUB 3 rendering directly with CoreText, including reflowable text, fixed layouts, media overlays, and bidirectional content. It shows both the control and the complexity involved in owning a native text-rendering pipeline. 📍Level: Advanced The Curious Case of the missing SwiftUI ClicksA real-time debugging log of SwiftUI buttons that quietly stop responding inside a horizontal ScrollView — fixed, but still without a clear answer for why. A fitting closer for this week's theme: sometimes going under the hood just leaves you with a better mystery. 📍Level: Intermediate SwiftUI Lies: Your Animation Breaks Because One View Is Actually Multiple LayersA first-person debugging story showing why a button’s label and background can animate independently — and how ZStack, drawingGroup, compositingGroup, and geometryGroup each solve (or half-solve) the problem for different reasons. A concrete companion to this week’s “nothing is as simple as it looks” theme. 📍Level: Intermediate This Week in Those Who Swift 🗞️The latest across Swift, Apple, AI, and the community. Swift Around the Web 🌐IP and DNS Leaks in WebKit Affecting Proxy Browsers and Apple iCloud Private RelayResearchers document a WebKit issue that can expose a user’s real IP address and DNS queries while using proxy-based browsers or iCloud Private Relay. Important context for teams making privacy guarantees around WebKit-based experiences. 📍Level: Intermediate Coding 👨💻How to stream SSE with URLSession in SwiftA practical implementation of Server-Sent Events using 📍Level: Intermediate Type-safe JSON and JSONB in StructuredQueriesStructuredQueries 0.35 introduces schema-checked support for JSON and JSONB data in SQLite. The article shows how to retain type safety while working with semi-structured local data. 📍Level: Advanced Using Top Functions Mode in Instruments to Quickly Find the Slowest CodeA concise guide to the Top Functions view in Xcode 26.4’s profiling instruments. Sorting by self-weight and inspecting flame graphs can make it much easier to identify where execution time is actually being spent. 📍Level: Intermediate Installing simulator runtimes from the command lineCommand-line steps for installing simulator runtimes when Xcode 27 beta remains stuck on “fetching download information.” A useful workaround to keep nearby when the graphical installer fails. 📍Level: Intermediate Sendable and @Sendable closures explained with code examplesA clear explanation of 📍Level: Intermediate Taking control of toolbar items in SwiftUIExplores SwiftUI toolbar placement, customization, and platform-specific behavior. Helpful for interfaces where the default toolbar layout does not provide enough control or consistency. 📍Level: Intermediate Apple 🍏Get ready for new creative assets on the App StoreApple previews new creative and marketing asset options for App Store product pages. Worth reviewing before planning your next product-page update or launch campaign. TestFlight UpdateThe latest TestFlight release notes, covering recent changes to Apple’s beta-distribution workflow. A quick check before your next external-testing cycle may save some surprises. AI & Tooling 🤖Using Cursor in Xcode 27A hands-on guide to connecting Cursor to Xcode 27 through Agent Client Protocol support. It offers an early look at how external coding agents can participate directly in an Xcode-based workflow. 📍Level: Intermediate Build a Local Codex Token Usage Ledger Without Replay ErrorsA practical fix for tracking token usage across Codex/Claude coding-agent sessions without hitting replay errors — useful if AI agents are part of your build pipeline, even outside the Swift/iOS-specific tooling this newsletter usually covers. 📍Level: Intermediate Tutorials 📒Recording VoiceOver on iOS & macOSA practical guide to capturing VoiceOver audio for accessibility testing, bug reports, and demos. iOS supports the workflow through screen recording, while macOS requires a virtual-audio device. 📍Level: Intermediate Community🤝SwiftUI should become Open-SourceMakes the case that open-sourcing SwiftUI could help developers diagnose and address long-standing issues such as keyboard focus and drag-and-drop. Even if the proposal feels unlikely, the argument raises useful questions about framework transparency and community participation. 📍Level: Intermediate Thanks for reading Those Who Swift! Subscribe for free to receive new posts. 👇
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