AgnosticSafeArea.swift

//
//  AgnosticSafeArea.swift
//

import UIKit

extension UIViewController {

    /**
     Auxiliary version-agnostic safe area layout guide
     */
    var safeLayoutGuide: UILayoutGuide {
        if #available(iOS 11.0, *) {
            return view.safeAreaLayoutGuide
        } else {
            let identifier = "safeAreaGuide"
            if let layoutGuide = view.layoutGuides.first(where: { $0.identifier == identifier }) {
                return layoutGuide
            } else {
                let layoutGuide = UILayoutGuide()
                layoutGuide.identifier = identifier
                view.addLayoutGuide(layoutGuide)
                NSLayoutConstraint.activate([
                    layoutGuide.topAnchor.constraint(equalTo: topLayoutGuide.bottomAnchor),
                    layoutGuide.leadingAnchor.constraint(equalTo: view.leadingAnchor),
                    layoutGuide.trailingAnchor.constraint(equalTo: view.trailingAnchor),
                    layoutGuide.bottomAnchor.constraint(equalTo: bottomLayoutGuide.topAnchor)
                ])
                return layoutGuide
            }
        }
    }
}