Open Radar

 
Area:
UIKit

Summary:

Presenting a `.formSheet` modal view controller that supports all / default orientations from a view controller that has `.portrait` as the only supported orientation can lead to a crash. This occurs only on devices that have a regular size class in Landscape.

Steps to Reproduce:

(Note - original radar has a sample application attached, the following section has been modified to provide clarity on open radar without the sample application)

- Create a single view application
- Embed the main view controller within a navigation controller
- Set the supported orientations of the main view controller as `.portrait`
- Create another view controller - modal view controller
- Leave the supported orientations of the modal view controller set to default (i.e. don't override it)
- Add a button to the main view controller's view to trigger the presentation of the modal view controller with a `.formSheet` `modalPresentationStyle`

```swift
    @IBAction func didTapPresent(_ sender: UIButton) {
        let modalViewController = ModalViewController()
        modalViewController.modalPresentationStyle = .formSheet
        present(modalViewController, animated: true, completion: nil)
    }

```

- Launch the sample application on a Plus device (or XS Max / XR)
- Rotate the device / simulator to landscape
- Tap the button

Expected Results:

The app should not crash

Actual Results:

The app crashes (hits an internal UIKit assert)

```
[Assert] transitionViewForCurrentTransition is not set! (<_UIFullscreenPresentationController: 0x7ff9be4023d0>)
```

Version/Build:

- iPhone 7 plus (iOS 12.1) / iPhone XS Max (iOS 12.1)
- Xcode Version 10.2 (10E125)