Hi,
When adapting an existing UIKit app for iPhone Duo, what should we consider the source of truth for layout adaptation at runtime?
For example, suppose the same scene transitions from a narrow layout to an unfolded layout where there is enough space to present two content regions side by side.
In this situation, should we primarily react to:
trait changes such as horizontalSizeClass changes to the view/window bounds safe area changes or a Duo-specific posture/hinge API?
We would like to avoid device-specific logic such as checking whether the current device is an iPhone Duo, and instead make the UI respond to the appropriate UIKit environment signals.
I'm also curious about view controller containment during these transitions. If the compact layout presents content through a single navigation hierarchy, but the unfolded layout can present multiple regions simultaneously, is the recommended approach to keep the same view controller hierarchy and adapt its layout, or is transitioning between different container view controller configurations expected?
In general, what is the recommended UIKit pattern for deciding when a structural UI adaptation should happen and which system signal should drive it?
Thanks!
Hello @sariogluemre ,
Starting with iOS 27, your iPhone app can be resized on iPad and on the Mac using iPhone Mirroring. Your app's layout should adapt to different screen sizes, so please don't think only about iPhone Duo when it comes to app resizability. Watch the WWDC26 video "Modernize your UIKit app" to learn more.
https://developer.apple.com/videos/play/wwdc2026/278
Our recommendation is to avoid device-specific logic, and embrace size classes to update your layout. Your app should support all device orientations.
UINavigationSplitView is a container that automatically adapts to changes in size classes, and also adapts to the fold on iPhone Duo.
For more information, check out the "Prepare your app for iPhone Duo" and "Strike a pose with adaptive layouts on iPhone Duo" videos released earlier this month.
