A Playground showcasing the iOS 13 system colors grayscale

grayscaleSystemColors.swift

//
//  System Colors Playground
//  fivestars.blog
//
//  Created by Federico Zanetello on 9/6/19.
//

import UIKit
import PlaygroundSupport

final class ContainerViewController: UIViewController {

  lazy var lightViewController: ColorViewController = {
    $0.overrideUserInterfaceStyle = .light
    return $0
  }(ColorViewController())

  lazy var darkViewController: ColorViewController = {
    $0.overrideUserInterfaceStyle = .dark
    return $0
  }(ColorViewController())

  override func loadView() {
    super.loadView()

    let stackView = UIStackView()
    stackView.distribution = .fillEqually
    stackView.axis = .vertical

    stackView.addArrangedSubview(lightViewController.view)
    stackView.addArrangedSubview(darkViewController.view)

    view = stackView
  }
}

class ColorViewController : UIViewController {
  private let systemColors: [UIColor] = [.systemGray,
                                         .systemGray2,
                                         .systemGray3,
                                         .systemGray4,
                                         .systemGray5,
                                         .systemGray6]
  override func loadView() {
    super.loadView()
    
    let horizontalStackView = UIStackView()
    horizontalStackView.distribution = .fillEqually

    for color in systemColors {
      let view = UIView()
      view.backgroundColor = color
      horizontalStackView.addArrangedSubview(view)
    }

    view = horizontalStackView
  }
}

let containerViewController = ContainerViewController()
containerViewController.preferredContentSize = CGSize(width: 600, height: 100)
PlaygroundPage.current.liveView = containerViewController