Weekly note ✏️
Apple announced a foldable iPhone this week and gave developers about six weeks before it ships. This issue looks at what that means for iOS developers: what we can safely work on now, what’s still uncertain, and where it may make sense to wait.
Are you starting the refactor now, or waiting for Xcode 27.1?
Shipping for Hardware You Can't Fully Test Yet
with Divya Ravi — Technical Editor
Apple announced the foldable iPhone on September 9 and gave developers about six weeks before it reaches customers. The interesting part isn’t just learning the new APIs. It’s figuring out what’s safe to change while the platform is still evolving.
It’s easy to treat this as an API-learning exercise: learn the new size classes, reserved regions, ArrangementViews, and start updating layouts. But the harder part is that we still don’t know everything. Some APIs are still coming through the Xcode 27.1 beta, and developers haven’t had real hardware to validate how apps behave across different fold positions.
So the real question is: how much should you build now?
I’ve made both mistakes. Earlier in my career, I rebuilt a navigation layer around a beta API that changed significantly before GM. That meant weeks of rework. I’ve also waited too long on a new platform capability and ended up playing catch-up after launch.
For iPhone Duo, I’d split the work into two buckets.
The safe stuff: move away from orientation checks, use size classes properly, and look for hardcoded screen dimensions or aspect-ratio assumptions. None of this is really foldable-specific. It’s good iOS engineering that the new form factor makes more important.
The uncertain stuff: anything that depends on the exact behavior of the hinge, fold positions, or APIs that are still changing. That’s where I’d wait. Building against a stable API is a one-time cost. Building against something that changes every beta can mean repeated rework.
There’s a broader lesson here too. Platforms are never really finished; they just usually feel finished because we don’t see the seams. A new form factor makes those seams obvious.
For me, the approach is simple: make the changes that are clearly correct today, and keep the hardware-specific pieces flexible until we know more.
What are you doing—starting now, or waiting for Xcode 27.1?
Related reading on this week's theme 📚
Apple’s iPhone Duo developer resources landed September 9, and there’s already a lot of discussion around what developers should actually do with them.
Here are four takes I found useful, each looking at a different part of the problem.
iPhone Duo for Developers: The 1.42 Problem and the SDK Gap
A detailed look at the display specs and the current SDK situation. It’s particularly useful if you want to understand what’s available today versus what’s still coming in Xcode 27.1.
📍Level: Advanced
iPhone Duo: First Developer Good-to-Knows
Jordan’s practical summary of Apple’s six Tech Talks. It covers the things most developers will care about first: adaptive layouts, safe areas, camera behavior, and multitasking.
📍Level: Intermediate
iPhone Duo for iOS Developers: What Actually Changes in Your Swift Code
A more code-focused walkthrough covering size classes, reserved regions, and ArrangementViews. Good if you want to get straight to the API changes.
📍Level: Intermediate
How Much Should Developers Invest in iPhone Duo?
A useful counterpoint to the “start preparing immediately” approach. It looks at expected adoption and the engineering cost of supporting another form factor.
📍Level: Intermediate
This Week in Those Who Swift 🗞️
The latest across Swift, Apple, AI, and the community.
Swift Around the Web 🌐
What Apple's September 2026 Event Means for Developers
A broader look at Apple’s September announcements, including the A20 Pro, on-device AI, AirPods 5, and the new Watch hardware.
📍Level: Beginner
Native is now the future of mobile at Shopify
Shopify explains its move from React Native back to native Swift and Kotlin. The interesting part is the economics: AI coding tools have changed how the team thinks about maintaining native codebases.
Not directly related to iPhone Duo, but definitely worth reading if you’re thinking about where AI-assisted development is taking mobile engineering.
📍Level: Beginner
Coding 👨💻
When Intuition Lies: Lessons from a CSV Parser
A good reminder that performance problems aren’t always where we expect them. The example starts with a CSV parser that looks reasonable but spends most of its time on string allocation rather than file I/O.
Also interesting: the release build was dramatically faster than debug.
📍Level: Intermediate
Action Runner: An iOS Architecture for Isolating Business Logic
A different approach to keeping business logic away from controllers. The Action/RunnableAction pattern and shared RunContext are worth looking at if your architecture is starting to develop circular dependencies.
📍Level: Advanced
iOS 27: CrashReportExtension Framework
A look at Apple’s new crash-reporting extension in iOS 27. Instead of doing everything from a signal handler, the crash can be inspected from a separate system-managed process.
📍Level: Advanced
In-House Over-the-Air Localizations in a Modular iOS App
An interesting production example from Just Eat Takeaway: updating localized strings remotely without requiring a full App Store release.
📍Level: Advanced
Apple 🍏
Get ready for iPhone Duo
Apple’s main developer hub for iPhone Duo. It brings together the six Tech Talks, Group Labs, Q&A sessions, and the Xcode 27.1 beta.
App Store submissions now open for the latest OS releases
Xcode 27 RC is available, and App Store Connect is accepting submissions built against the latest OS releases. The new minimum-SDK requirements take effect across Apple platforms in April 2027.
AI & Tooling 🤖
LazyState 1.0: Now Available to Everyone
Point-Free’s LazyState macro is now at 1.0. It creates SwiftUI state lazily and keeps it tied to the view’s identity.
📍Level: Intermediate
Object Tracking Updates in visionOS 27 and iOS 27
A look at the new object-tracking capabilities in visionOS 27 and iOS 27, including an accessibility project that combines object tracking with Vision Pro and iPhone.
📍Level: Intermediate
Design🎨
Designing for iPhone Duo: The HIG Guide in 5 Minutes
A quick walkthrough of Apple’s HIG guidance for the new form factor, including adaptive layouts, safe areas, fold displacement, and the new arrangement containers.
📍Level: Intermediate
Tutorials📒
Moving from XCTest to Swift Testing
A practical guide to moving from XCTest to Swift Testing, including the new @Suite and @Test APIs and updated assertion syntax.
📍Level: Beginner
Video 🎥
Prepare your app for iPhone Duo
If you only watch one of Apple’s six iPhone Duo videos, I’d start here. It covers flexible layouts, size classes, asymmetric safe areas, and the reserved-regions API..
📍Level: Intermediate
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