Medium_ProgrammaticallyUI_base_ViewController_structure.swift

import UIKit

class FirstViewController: UIViewController {
  private let topicLabel: UILabel = {
	  let label = UILabel()
	  label.text = "Topic"
	  label.textAlignment = .center
	  label.translatesAutoresizingMaskIntoConstraints = false
		
	  return label
  }()
	
  // MARK: - View lify-cicle
  override func viewDidLoad() {
    super.viewDidLoad()
		
    buildUI()
  }
	
  // MARK: - Private methods
  private func buildUI() {
    view.backgroundColor = .white
		
    view.addSubview(topicLabel)
		
    NSLayoutConstraint.activate([
      topicLabel.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor),
      topicLabel.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor),
      topicLabel.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor),
    ])
  }
}