topLayoutGuide in child view controller

Question

I have a UIPageViewController with translucent status bar and navigation bar. Its topLayoutGuide is 64 pixels, as expected.

However, the ch

Answer 1

This is an unfortunate behavior that appears to have been rectified in iOS 11 with the safe-area API revamp. That said, you will always get the correct value off the root view controller. For example, if you want the upper safe area height pre-iOS 11:

Swift 4

let root = UIApplication.shared.keyWindow!.rootViewController!
let topLayoutGuideLength = root.topLayoutGuide.length