Craig Hockenberry4d ago

Heads up for folks looking at resizable iPhone apps on iOS 27:

If you use constraint variations in your storyboards to detect compact/regular widths, you have a lot of rework in your future. That is because on iPhone the horizontalSizeClass is always compact and your storyboard layouts will not change when the UI is resized. Instead, you will have to track size changes and update constraints in your own code.

Initially I thought this was a bug, but it's not: https://fatbobman.com/en/posts/from-size-class-to-available-space/

Show threadCraig Hockenberry4d ago

Unfortunately, this major change to storyboards wasn't explicitly stated in the "Modernize your UIKit app" video.

Also, there is no warning while compiling the storyboard or a runtime indication that something that used to work now doesn't.

I never liked the idea of size classes, and I like them even less now. But they were the "right" way to do things - and now they are "wrong". Grrrr.

https://developer.apple.com/videos/play/wwdc2026/278/

Modernize your UIKit app - WWDC26 - Videos - Apple Developer

Discover the latest updates to UIKit. Learn how to update your iPhone app layouts to work great when resized with iPhone Mirroring and on...

Apple Developer
Show threadCraig Hockenberry

For an app with a reasonable amount of interface complexity (e.g. a UI that adapts between a portrait layout and a tablet landscape layout) there are A LOT of these constraint variations.

And the only way to find/fix them is by digging through that complex interface's storyboard.

Time consuming & error prone & a pain in the ass. The irony is the folks who treated the iPad as a big iPhone had it right all along 😫

Jun 24 at 10:31pmIvory for Mac
Show threadCraig Hockenberry3d ago

UIKit engineers: here's your chance to explain what the hell is going on with horizontalSizeClass and to hopefully improve the developer experience behind the change.

https://developer.apple.com/forums/thread/836088

Horizontal Size Classes on iPhone … | Apple Developer Forums

Show threadCraig Hockenberry2d ago

I'm wondering if all this confusion about horizontal size classes is due to buggy behavior in the Device Hub simulator.

I'm only running Xcode 27 in a VM for now, so the Device Hub can't connect to a physical device (no Wi-Fi). All I have are simulated devices.

If someone can run this on a physical device, it would be nice to know if it works or not.

https://developer.apple.com/forums/thread/836088?answerId=895582022#895582022

Horizontal Size Classes on iPhone … | Apple Developer Forums

Show threadNico Reese2d ago
@chockenberry Looks like you cannot resize a physical device in Device Hub. And I don't have iPhone Mirroring in the EU... What's Apple's idea on how we should test this properly?
Show threadjoe kimberlin2d ago
@chockenberry have you tried this on the 17 pro max simulator? i see .regular when resized there.
Show threadCraig Hockenberry2d ago
@Joekw That is default state for that device. I chose 17 for a reason.
Show threadjoe kimberlin2d ago
@chockenberry default state? it’s .compact by default, no?
Show threadCraig Hockenberry2d ago

@Joekw I see what you mean now - I was thinking about it's rotated orientation.

My main goal here is to show a failure state and not a workaround.

Show threadOleg Shanyuk 🇺🇦3d ago
@chockenberry yeah. This video for UIKit changes is the most critical for wwdc26. Apple was deprecating and warned about “this day will come” for ten years or so. Now they did it. And yeah, we also having a trouble now 🫡😅