PtitChevreuil

extension UIViewController {
    var safeTopAnchor: NSLayoutYAxisAnchor {
        if #available(iOS 11.0, *) {
            return view.safeAreaLayoutGuide.topAnchor
        } else {
            return topLayoutGuide.bottomAnchor
        }
    }
 
    var safeBottomAnchor: NSLayoutYAxisAnchor {

PtitChevreuil

extension UIView {
    var safeTopAnchor: NSLayoutYAxisAnchor {
        if #available(iOS 11.0, *) {
            return safeAreaLayoutGuide.topAnchor
        } else {
            return 0
        }
    }
 
    var safeBottomAnchor: NSLayoutYAxisAnchor {

PtitChevreuil

extension UIViewController {
    var compatibleSafeInsets: UIEdgeInsets {
        if #available(iOS 11, *) {
            return view.safeAreaInsets
        } else {
            return UIEdgeInsetsMake(topLayoutGuide.length, 0, bottomLayoutGuide.length, 0)
        }
    }
}

PtitChevreuil

// in your UIViewController

func setupMySubview() {
  let topInset = compatibleSafeInsets.top
  let bottomInset = compatibleSafeInsets.bottom
  let leftInset = compatibleSafeInsets.left
  let rightInset = compatibleSafeInsets.right
  let height = view.frame.size.height - bottomInset - topInset
  let width = view.frame.size.width - leftInset - rightInset
  

PtitChevreuil

myButton.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor, multiplier: 1.0)