view.traitCollection.horizontalSizeClass returning undefined (0) in viewDidLoad

Question

I\'m using a UITextView inside a UIPageViewController, and I want to determine the font size based on the size class of the device.

The first slide of the page view is l

Answer 1

I took a hint from this Apple Technical Q&A and used viewWillLayoutSubviews instead of viewDidLoad/viewWillAppear.