Simple implementation of a side menu using a UIView.

SideMenuViewController.swift

//  Simple implementation of a side menu using a UIView.
//  I would rather use a new controller to build that menu and add it as a child to this one using the addChild(_ childController: UIViewController) method, but out of scope here.

import UIKit
import PlaygroundSupport

class SideMenuViewController: UIViewController {

    private var menuBarButtonItem: UIBarButtonItem!

    private let sideMenu: UIView = {
        let view = UIView()
        view.translatesAutoresizingMaskIntoConstraints = false
        view.backgroundColor = UIColor.black.withAlphaComponent(0.4)
        return view
    }()

    private var isMenuShowing: Bool = false {
        willSet {
            animateMenu(newValue)
            handleMenuBarButtonItemTitle(newValue)
        }
    }

    var sideMenuLeftConstraint: NSLayoutConstraint!

    enum SideMenuSettings {
        static let width: CGFloat = 200
        static let animationTime = 0.3
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        title = "Side Menu"
        view.backgroundColor = .white
        setupNavigationBar()
        setupViews()
    }

    private func setupNavigationBar() {
        menuBarButtonItem = UIBarButtonItem(title: nil, style: .done, target: self, action: #selector(handleMenu))
        navigationItem.leftBarButtonItem = menuBarButtonItem
        handleMenuBarButtonItemTitle(isMenuShowing)
    }

    private func handleMenuBarButtonItemTitle(_ isShowing: Bool) {
        let title = isShowing ? "Close" : "Open"
        menuBarButtonItem.title = title
    }

    private func setupViews() {
        view.addSubview(sideMenu)

        sideMenuLeftConstraint = sideMenu.leftAnchor.constraint(equalTo: view.leftAnchor, constant: -SideMenuSettings.width)
        NSLayoutConstraint.activate([
            sideMenu.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor),
            sideMenuLeftConstraint,
            sideMenu.bottomAnchor.constraint(equalTo: view.bottomAnchor),
            sideMenu.widthAnchor.constraint(equalToConstant: SideMenuSettings.width),
        ])
    }

    @objc
    public func handleMenu() {
        isMenuShowing.toggle()
    }

    private func animateMenu(_ isShowing: Bool) {
        sideMenuLeftConstraint.constant = isShowing ? 0 : -SideMenuSettings.width
        UIView.animate(withDuration: SideMenuSettings.animationTime,
                       delay: 0,
                       options: .curveEaseOut,
                       animations: {
            self.view.layoutIfNeeded()
        })
    }
}

let viewController = UINavigationController(rootViewController: SideMenuViewController())
PlaygroundPage.current.liveView = viewController
PlaygroundPage.current.needsIndefiniteExecution = true