Safe area layout

SafeAreaLayout.swift

class ViewController: UIViewController {

    let wrapperView = UIView()
    let cyanView = UIView()

    override func viewDidLoad() {
        view.backgroundColor = .yellow
        view.addSubview(wrapperView)
        wrapperView.addSubview(cyanView)

        wrapperView.backgroundColor = .red
        wrapperView.translatesAutoresizingMaskIntoConstraints = false

        cyanView.backgroundColor = .cyan
        cyanView.translatesAutoresizingMaskIntoConstraints = false
        applyConstraints()
    }

    func applyConstraints() {
        let guide = view.safeAreaLayoutGuide
        wrapperView.topAnchor.constraint(equalTo: guide.topAnchor).isActive = true
        wrapperView.leadingAnchor.constraint(equalTo: guide.leadingAnchor).isActive = true
        wrapperView.trailingAnchor.constraint(equalTo: guide.trailingAnchor).isActive = true
        wrapperView.bottomAnchor.constraint(equalTo: guide.bottomAnchor).isActive = true

        let margins = wrapperView.layoutMarginsGuide
        cyanView.topAnchor.constraint(equalTo: margins.topAnchor).isActive = true
        cyanView.leadingAnchor.constraint(equalTo: margins.leadingAnchor).isActive = true
        cyanView.trailingAnchor.constraint(equalTo: margins.trailingAnchor).isActive = true
        cyanView.bottomAnchor.constraint(equalTo: margins.bottomAnchor).isActive = true
    }
}