What is UITransitionView about?

I was using Xcode’s View Hierarchy and noticed this UITransitionView in my view hierarchy.

...
    UIWindow
        UITransitionView
            FooVC
        UITransitionView
            BarVC

This was odd because I was expected a view hierarchy as such:

...
    UIWindow
        UITransitionView
            FooVC
                BarVC

What made it more perplexing was that the canvas was showing things correct, but the View Hierarchy didn’t make sense.

To be clear on jargon, the following is the name of each section of Apple’s view debugger:

View Debug Hierarchy

I googled Apple documents, but found nothing on UITransitionView. It’s private API. I had suspicions for why I was seeing it… So I opened up a sample project to test things out.

The following is the view hierarchy I got for presenting the yellow VC on another VC.

Expanded Hierarchy is as such:

UITransitionView in View Debugger Hierarchy

Conclusion

If you you’re seeing multiple UITransitionView it’s likely because you’re presenting one viewcontroller over another. One UITransitionView is for the presenting nav stack while the other is for the presented nav stack.

Conclusion#

Conclusion