Open Radar

 
Summary:
Background information:

Our application's main interface is dark, and hence we use UIStatusBarStyleLightContent for our main view controller's -preferredStatusBarStyle.

Often, we will present child view controller as a modal form sheet.  

As a form sheet, we still want UIStatusBarStyleLightContent (as the dark parent controller is visible).  However, in a horizontal compact environment, the view controller will appear full screen.  Due to the whiteness of the VC, it returns UIStatusBarStyleDefault for -preferredStatusBarStyle to make the status bar black.

Unfortunately, UIKit will often get very confused whether it should be displaying the white status bar or black status bar.  After a lot of diagnosis, we traced this to orientation changes that result in different horizontalSizeClass.

To demonstrate this, run the attached sample project on an iPad Air 2 or iPhone 6 Plus.

1. Start in portrait orientation (on the 6 Plus), or portrait 438w on the iPad.
2. Show the child VC
3. Rotate the device to landscape
4. Dismiss the child VC

The status bar is now black-on-dark-gray until the reverse steps are taken:

5. Show the child VC
6. Rotate back to portrait
7. Dismiss the child VC

Under the hood, step #2 sets the ChildVC as the -_presentedStatusBarViewController of the root view controller.  This would normally be set to nil in step #4; however, due to the orientation change, it is never cleared.

Since _presentedStatusBarViewController is a strong reference, UIKit will keep ChildVC alive even after the main view controller is dismissed/popped.  This burned us multiple times during iOS 9 adoption, as one of our VCs deep in the hierarchy was still alive even when the user returned to our root.

Steps to Reproduce:
(See description)

Expected Results:
1. The status bar always uses the -preferredStatusBarStyle of the view controller underneath it.
2. UIKit doesn't keep a strong reference to my child view controller long after it has been dismissed.

Actual Results:
1. Status bar is the wrong color
2. My view controller is kept alive until something knocks it out of _presentedStatusBarViewController

Version:
iOS 9.0, iOS 9.1 beta 1