At what stage of the UIViewController lifecycle is it recommended to work with the already calculated sizes of its View?

Working with already calculated View sizes in UIViewController is recommended in the viewDidLayoutSubviews() method. At this stage, the system has already calculated and set the sizes and positions of all subviews, including the main View of the controller.

If you try to get the View sizes in viewDidLoad() or viewWillAppear(), the sizes may not be set yet or may be zero.

Example usage:

override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()
    let width = view.frame.size.width
    let height = view.frame.size.height
    // You can safely work with sizes here
}