Modal View Controller with constraints

modal.swift

//: Playground - noun: a place where people can play

import UIKit
import PlaygroundSupport

var str = "Hello, playground"

class MainViewController: UIViewController {

  let button: UIButton = {
    let button = UIButton(frame: .zero)
    button.backgroundColor = .blue
    button.setTitle("Press Me", for: .normal)
    button.translatesAutoresizingMaskIntoConstraints = false
    return button
  }()

  init() {
    super.init(nibName: nil, bundle: nil)
    setup()
  }
  
  required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
  }

  private func setup() {

    view.backgroundColor = .white
    view.addSubview(button)

    button.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 30).isActive = true
    button.rightAnchor.constraint(equalTo: view.rightAnchor, constant: -30).isActive = true
    button.topAnchor.constraint(equalTo: view.topAnchor, constant: 100).isActive = true
    button.heightAnchor.constraint(equalToConstant: 50).isActive = true
    button.addTarget(self, action: #selector(showModal), for: .touchUpInside)

  }

  func showModal() {

    let modalVC = ModalViewController()
    present(modalVC, animated: true, completion: nil)

  }

}

class ModalViewController: UIViewController {

  let innerView: UIView = {
    let innerView = UIView(frame: .zero)
    innerView.backgroundColor = .red
    innerView.translatesAutoresizingMaskIntoConstraints = false
    return innerView
  }()

  init() {
    super.init(nibName: nil, bundle: nil)
    setup()
  }
  
  required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
  }

  private func setup() {

    view.backgroundColor = .white
    view.addSubview(innerView)

    innerView.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 17).isActive = true
    innerView.rightAnchor.constraint(equalTo: view.rightAnchor, constant: -17).isActive = true
    innerView.topAnchor.constraint(equalTo: view.topAnchor, constant: 17).isActive = true
    innerView.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -17).isActive = true

    let tapGesture = UITapGestureRecognizer()
    tapGesture.addTarget(self, action: #selector(closeModal))
    innerView.addGestureRecognizer(tapGesture)

  }

  func closeModal() {

    dismiss(animated: true, completion: nil)

  }

}

let vc = MainViewController()

PlaygroundPage.current.liveView = vc