Nil Coalescing Newsletter - October 2026

Nil CoalescingOct 31, 2026

Nil Coalescing Newsletter - October 2026

Hi there,

I hope you've had a good October! For us, this month has been all about iPhone Duo. I had the amazing opportunity to travel to Sydney (twice!) to test our apps on the device ahead of its release, and much of my writing this month has focused on adapting SwiftUI interfaces to the new form factor.

There have been some exciting developments with our apps, too. I launched Whio, a new ebook reader for technical EPUBs and PDFs on iPhone and iPad, and Matt and I have been working on improvements to SwiftFairy, including a new Scroll for checking SwiftUI layouts. And this week, my coffee app Breve was featured as App of the Day on the US App Store!

In this issue, I'll share more about what we've been working on, my latest articles on iPhone Duo, and some special offers I've put together for you.

Whio: a reader built for technical books

I've been writing technical books for several years, and I've never been happy with how traditional ebook readers handle them. Code examples lose their syntax highlighting and indentation, copying code accurately can be difficult, and PDFs are particularly hard to read on a phone. I provide online versions of my books with a better reading experience, but many people still prefer to download them and read offline, on their commute, in cafes, or wherever they have time. I wanted an app that gives technical content the attention it needs in those settings too, so I built Whio.

In Whio, code examples keep their syntax highlighting and indentation, scroll horizontally instead of wrapping, and have their own font, size, and theme settings, along with zoom and copy controls. PDFs are turned into reflowable books, so the text adapts to the screen instead of staying on fixed-size pages, and this works with scanned PDFs too.

Code examples with syntax highlighting in Whio on iPhone

Accessibility was an important focus from the start, particularly for readers with dyslexia. Matt has dyslexia, and his feedback has helped me develop and refine features such as letter distinction, which adds space between letters that can blend together and varies their emphasis, and a reading guide that underlines the current line or keeps a few lines in focus while dimming the rest.

The reading guide in Whio on iPhone Duo

iPhone Duo was also part of what inspired me to build Whio. It's small enough to carry everywhere but opens into a wider reading surface. At the Apple workshops in Sydney, I was able to test Whio on the device and receive feedback from Apple's designers.

You can read more about the features and the story behind the app in my post Introducing Whio: a reader built for technical books. Whio is free to download on the App Store and includes three illustrated books, so you can try the reading experience before importing your own. Whio Unlimited unlocks reading your own DRM-free EPUBs and PDFs, with a subscription or a one-time purchase.

I've just released the first update, Whio 1.0.1. It lets you import several books at once, groups highlights and notes by book in the notebook, opens more EPUBs and PDFs, loads PDFs faster, and recognizes and highlights code in more books and languages.

With this update, I've also adjusted the pricing based on the feedback I received after launch. And as a thank you for being a newsletter subscriber, you can get lifetime access to Whio Unlimited at a special price, you'll find the details at the end of this issue. I'm also working on the infrastructure to automatically offer this special lifetime price to everyone who has purchased any of our books, or will purchase one in the future.

SwiftFairy: SwiftUI Layout & Resizability

With iPhone Duo introducing new screen configurations and Apple placing greater emphasis on resizable windows on iPad and overall app quality, it's more important than ever to make sure our apps adapt well to different devices, window sizes, and text sizes. Unfortunately, coding agents still struggle with adaptive SwiftUI layouts, often hardcoding dimensions or making assumptions about the available space.

To help with that, we've brought together everything we know about SwiftUI layout, drawing on my experience working on SwiftUI at Apple, what we've learned from building our own apps, and insights I gained from Apple engineers in Sydney. We've turned all of this into a new SwiftFairy Scroll: SwiftUI Layout & Resizability. It checks for over 100 potential issues, from fixed frames that prevent text from wrapping to uses of GeometryReader where a layout or scrolling API would be more appropriate.

A SwiftFairy finding flagging a layout issue

The Scroll also includes rules for iPhone Duo. For example, agents often reach for onHingeChange() whenever they need to adapt an interface to the device, including for layout, where it causes unnecessary updates and doesn't tell the view where the fold is. SwiftFairy guides them to the most appropriate API for each case.

Alongside the new Scroll, we've updated Proper SwiftUI, Modern Swift, and Performant Swift Charts, and made audits much faster for large projects. You can find all the details in the release notes.

If you'd like to give it a try, as a newsletter subscriber you can get 20% off any plan for any Scroll with a special discount code at the end of this issue.

New blog posts this month

Most of my posts this month cover the new SwiftUI APIs for iPhone Duo, from presenting sheets and arranging content around the fold to driving animations with the hinge angle. I was also very happy to hear my post about ArrangementView mentioned during one of Apple's iPhone Duo group labs.

ArrangementView in SwiftUI: split and overlay layouts for iPhone Duo

Learn how ArrangementView places two related views side by side, stacked, or layered depending on the available space and the fold, and how to configure the result with split and overlay styles.

Presenting SwiftUI sheets on iPhone Duo

Review the automatic sheet adaptations SwiftUI makes on iPhone Duo, and learn how to configure sheet placement and toolbar arrangement to suit the content being presented.

Positioning SwiftUI views around the fold on iPhone Duo

Read the fold's position from SwiftUI's reserved regions and lay out grids around it, keeping the number of columns stable as the device folds and unfolds.

Driving SwiftUI animations with the hinge angle on iPhone Duo

Respond to hinge changes with the onHingeChange() modifier and drive animations and visual effects from the hinge angle as the device folds and unfolds.

Fix misaligned paging in SwiftUI scroll views

Prevent full-width pages in SwiftUI scroll views from drifting out of alignment by removing extra spacing between pages when using paging behavior.

Breve is App of the Day!

I was really happy to see my coffee app Breve featured as App of the Day on the US App Store this week! Apple published a lovely editorial story, Brew the Perfect Cup of Coffee, about Breve and my experience building it.

Breve featured as App of the Day on the App Store Today tab and its App of the Day story on iPhone

Earlier this month, Breve was also featured in the Great Apps Updated for iOS 27 collection on the App Store in New Zealand and Australia, so it's been a particularly exciting month for the app.

Over the last few months, I've been trying to plan app updates and in-app events further ahead and submit more feature nominations through App Store Connect. It's been really nice to see some of those nominations turn into actual App Store features, and they've definitely helped more people discover Breve.

Special offers for subscribers

Last but not least, as a thank you for subscribing to our newsletter, I've put together a few special offers for Whio, SwiftFairy, and our books.

Whio Unlimited

If you'd like to use Whio to read technical EPUBs and PDFs, you can get lifetime access to Whio Unlimited for US$29.99 with this special offer. It's a one-time purchase, so there's no subscription to worry about. You can also redeem the code SWIFTREADER directly in the app by opening More Options on the paywall screen.

Whio on iPad, iPhone Duo, and iPhone

SwiftFairy

If you're using coding agents for Swift or SwiftUI development, SwiftFairy can help them catch issues and improve their code, from API usage and performance to adaptive layouts. You can get 20% off any plan for any Scroll with the code OCT26SF until November 8, 2026.

You can find the available Scrolls and plans on the SwiftFairy purchase page.

The SwiftFairy review workflow with a coding agent

Swift and SwiftUI books

We're also offering 20% off all our Swift and SwiftUI books and bundles with the code OCT26BKS until November 8, 2026.

Whether you're interested in SwiftUI, Swift Charts, or improving your Swift code, there's plenty to choose from. Here's a quick overview of the books included in the offer:

Swift Charts Beyond the Basics — Build advanced data visualizations with custom composition, styling, and responsive interactions while preserving performance and accessibility.
The SwiftUI Way — Master recommended SwiftUI usage patterns and avoid common anti-patterns to build stable and performant production apps.
SwiftUI Fundamentals — Develop a deeper understanding of SwiftUI's core APIs and underlying mechanisms to use the framework effectively in your projects.
Swift Gems — Explore over 100 practical Swift tips for experienced developers looking to refine their skills.
Integrating SwiftUI into UIKit Apps — Discover practical techniques for introducing SwiftUI into existing UIKit projects.

You can also explore our ready-made bundles or build your own custom bundle if you'd like to get several books together. All book purchases include free lifetime updates.

Swift and SwiftUI books from Nil Coalescing, including Swift Charts Beyond the Basics

Thank you for reading and for your continued support! If you give Whio a try, I'd love to hear what you think.

Natalia

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