UIWindow+PrintHierarchy.swift

extension UIWindow {

    /// Print the app's key window hierarchy.
    class func printKeyWindowHierarchy() {
        UIApplication.shared.keyWindow?.printHierarchy()
    }
    
    /// Prints the window's view hierarchy.
    func printHierarchy() {
        traverseHierarchy { responder, level in
            print(String(repeating: " ", count: level * 2) + String(describing: responder))
        }
    }
}