LayoutGuides.swift

import UIKit

class TestViewController: UIViewController {

    let stackView: UIStackView = {
        let stackView = UIStackView()
        stackView.translatesAutoresizingMaskIntoConstraints = false
        stackView.axis = .vertical
        stackView.spacing = 16
        return stackView
    }()

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .white
        setupUI()
    }

    func addView(withColor color: UIColor, toLayoutGuide layoutGuide: KeyPath<UIView, UILayoutGuide>) {
        let aView = UIView()
        aView.backgroundColor = color.withAlphaComponent(0.5)
        aView.layer.borderColor = color.cgColor
        aView.layer.borderWidth = 3
        aView.translatesAutoresizingMaskIntoConstraints = false
        view.insertSubview(aView, belowSubview: stackView)
        constrainToLayoutMarginGuide(aView: aView, view: view, layoutGuide: layoutGuide)
        addLabel(rect: view[keyPath: layoutGuide].layoutFrame, color: color)
    }

    func constrainToLayoutMarginGuide(aView: UIView, view: UIView, layoutGuide: KeyPath<UIView, UILayoutGuide>) {
        NSLayoutConstraint.activate([
            aView.topAnchor.constraint(equalTo: view[keyPath: layoutGuide].topAnchor),
            aView.leadingAnchor.constraint(equalTo: view[keyPath: layoutGuide].leadingAnchor),
            aView.trailingAnchor.constraint(equalTo: view[keyPath: layoutGuide].trailingAnchor),
            aView.bottomAnchor.constraint(equalTo: view[keyPath: layoutGuide].bottomAnchor),
        ])
    }

    override func viewDidLayoutSubviews() {
        view.subviews.forEach {
            $0.removeFromSuperview()
        }
        stackView.arrangedSubviews.forEach {
            stackView.removeArrangedSubview($0)
            $0.removeFromSuperview()
        }
        setupUI()
    }

    func setupUI() {
        view.addSubview(stackView)
        NSLayoutConstraint.activate([
            stackView.centerXAnchor.constraint(equalTo: view.centerXAnchor),
            stackView.centerYAnchor.constraint(equalTo: view.centerYAnchor),
        ])
        addView(withColor: .systemBlue, toLayoutGuide: \.layoutMarginsGuide)
        addView(withColor: .systemGreen, toLayoutGuide: \.readableContentGuide)
        addView(withColor: .systemOrange, toLayoutGuide: \.safeAreaLayoutGuide)
    }

    func addLabel(rect: CGRect, color: UIColor) {
        let label = UILabel()
        label.font = .monospacedSystemFont(ofSize: 30, weight: .light)
        label.text = showCGRect(rect)
        label.numberOfLines = 2
        label.backgroundColor = color
        label.layer.borderColor = UIColor.white.cgColor
        label.layer.borderWidth = 0.5
        stackView.addArrangedSubview(label)
    }

    func showCGRect(_ cgRect: CGRect) -> String {
        let sizeClass = traitCollection.horizontalSizeClass
        return "x: \(cgRect.minX, sizeClass: sizeClass), w: \(cgRect.width, sizeClass: sizeClass)\ny: \(cgRect.minY, sizeClass: sizeClass), h: \(cgRect.height, sizeClass: sizeClass)"
    }
}

extension String.StringInterpolation {

    mutating func appendInterpolation(_ value: CGFloat, sizeClass: UIUserInterfaceSizeClass) {
        let decimals = sizeClass == .regular ? 4 : 3
        let string = String(format: "%\(decimals).0f", value)
        appendLiteral(string)
    }

}