Menu Delegate for easily handling a side drawer nav

MenuDelegate.swift

import UIKit

/// Fuctionality for a root view controller that handles the feature container view and the side menu drawer
protocol MenuDelegate: class {
    var titleLabel: UILabel! { get } // To show feature name in mock nav bar
    var containerView: UIView! { get }
    var menuWidthConstraint: NSLayoutConstraint! { get }
    var contentViewController: UIViewController! { get set }

    func showTimeline()
    func showProfile()
    func showMessages()
    func showSettings()
    func logout()
}

extension MenuDelegate where Self: UIViewController {

    func toggleMenu() {
        let isMenuVisible = menuWidthConstraint.constant > 0
        animateMenu(shouldShow: !isMenuVisible)
    }

    func animateMenu(shouldShow: Bool) {
        let newWidth = shouldShow
            ? Constants.Menu.menuWidth
            : 0

        view.layoutIfNeeded()
        menuWidthConstraint.constant = newWidth

        UIView.animate(withDuration: 0.5,
                       delay: 0,
                       usingSpringWithDamping: 0.7,
                       initialSpringVelocity: 0.25,
                       options: [.curveEaseInOut],
                       animations: { self.view.layoutIfNeeded() },
                       completion: nil)
    }

    func dismissSideMenu() {
        animateMenu(shouldShow: false)
    }

    func newContentViewController<T: UIViewController>(forClass classType: T.Type) -> T? {
        guard let nextViewController: T = StoryboardHelper.new() else {
            return nil
        }
        return nextViewController
    }

    func replaceOrRefreshContent<T>(with nextViewController: T) where T: UIViewController, T: TopLevelViewControllerType {
        if contentViewController is T,
            let refreshableVC = contentViewController as? DataRefreshable {

            // Refresh the current feature view when selected while already present
            refreshableVC.refreshData()
        } else {
            replaceContent(with: nextViewController)
        }

    }

    private func replaceContent<T>(with nextViewController: T) where T: UIViewController, T: TopLevelViewControllerType {
        removeContent()

        contentViewController = nextViewController
        addChildViewController(nextViewController)
        contentViewController!.view.frame = containerView.bounds
        contentViewController!.didMove(toParentViewController: self)
        containerView.addSubview(contentViewController!.view)
        titleLabel.text = nextViewController.navigationTitle

        view.layoutIfNeeded()
    }

    func removeContent() {
        if let content = contentViewController {
            content.willMove(toParentViewController: nil)
            content.view.removeFromSuperview()
            content.removeFromParentViewController()
            self.contentViewController = nil
        }
    }
}

MenuModel.swift

import UIKit

struct MenuModel {
    let text: String
    let image: UIImage?
    let handler: () -> Void
    
    init(text: String, image: UIImage? = nil, handler: () -> Void) {
        self.text = text
        self.image = image
        self.handler = handler
    }
}

ParentNavigationDelegate.swift

protocol ParentNavigationDelegate: class {
    func setNavBar(title: String)
}

ParentViewController.swift

import UIKit

/**
ParentViewController should be embedded in a UINavigationController in the Main storyboard. It will consist of two container views side by side. The left will contain a TableViewController for the SideMenuViewController and the right (`containerView`) will be the width of the device and house the `contentViewController`. A toolbar sits atop the containerView as a mock nav bar for the root views. 
*/
class ParentViewController: UIViewController, MenuDelegate {
    @IBOutlet weak var titleLabel: UILabel!
    @IBOutlet weak var containerView: UIView!
    @IBOutlet weak var menuWidthConstraint: NSLayoutConstraint!

    weak var contentViewController: UIViewController!
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        menuWidthConstraint.constant = 0
        navigationController?.isNavigationBarHidden = true
    }
    
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        navigationController?.isNavigationBarHidden = false
    }
    
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "embedInitialContent" {
            contentViewController = segue.destination
        } else if let menuVC = segue.destination as? SideMenuViewController {
            menuVC.delegate = self
        }
    }
    
    // MARK: - Navigation

    func showTimeline() {
        if let nextViewController = newContentViewController(forClass: TimelineViewController.self) {
            replaceContent(with: nextViewController)
        }
        dismissSideMenu()
    }

    func showProfile() {
        if let nextViewController = newContentViewController(forClass: ProfileViewController.self) {
            replaceContent(with: nextViewController)
        }
        dismissSideMenu()
    }

    func showMessages() {
        if let nextViewController = newContentViewController(forClass: MessagesViewController.self) {
            replaceContent(with: nextViewController)
        }
        dismissSideMenu()
    }

    func showSettings() {
        if let nextViewController = newContentViewController(forClass: SettingsViewController.self) {
            replaceContent(with: nextViewController)
        }
        dismissSideMenu()
    }
    
    func logout() {
        repository.logout()
        performSegue(withIdentifier: "unwindToLogin", sender: nil)
    }
}

// MARK: - Navigation Bar Handling

extension ParentViewController: MenuDelegate, ParentNavigationDelegate {

    @IBAction private func menuButtonPressed(_ sender: UIBarButtonItem) {
        toggleMenu()
    }

    func setNavBar(title: String) {
        titleLabel.text = title
    }

}

SideMenuViewController.swift

import UIKit

class SideMenuViewController: UIViewController {
    @IBOutlet weak private var tableView: UITableView!
    @IBOutlet weak private var versionLabel: UILabel!

    weak var delegate: MenuDelegate?

    /// Generated dynamically to show/hide elements depending on user state
    private var cellModels: [MenuModel] {
        guard let delegate = delegate else {
            return []
        }
        var models: [MenuModel] = []

        models.append((text: "Timeline", handler: delegate.showTimeline))
        models.append((text: "Profile", handler: delegate.showProfile))
        models.append((text: "Messages", handler: delegate.showMessages))
        models.append((text: "Settings", handler: delegate.showSettings))
        models.append((text: "Log Out", handler: delegate.logout))

        return models
    }
    
    var versionLabelText: String {
        guard let versionNumberString = Bundle.main.infoDictionary?["CFBundleShortVersionString"] as? String,
        let buildNumberString = Bundle.main.infoDictionary?["CFBundleVersion"] as? String else {
            return ""
        }
        return String(format: "Version %@ (%@)", versionNumberString, buildNumberString)
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        versionLabel.text = versionLabelText
    }

    /* If you have a dynamic side menu you can update it here
    override func viewWillLayoutSubviews() {
        super.viewWillLayoutSubviews()

        if delegate?.isMenuVisible == true {
            // Update cells as menu is being revealed
            tableView.reloadData()
        }
    }
    */

}

// MARK: - Table Handling

extension SideMenuViewController: UITableViewDataSource, UITableViewDelegate {

    func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return cellModels.count
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "MenuItemCell", for: indexPath)
        let model = cellModels[indexPath.row]

        cell.textLabel?.text = model.text
        cell.imageView?.image = model.image

        return cell
    }

    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        tableView.deselectRow(at: indexPath, animated: true)

        let model = cellModels[indexPath.row]
        model.handler()
    }
}

TopLevelViewControllerType.swift

import UIKit

/// Identifies a root View Controller for a menu feature. Since a custom nav bar replacement is used, this is needed to set the title.
protocol TopLevelViewControllerType {
    var navigationTitle: String { get }
}

This makes use of StoryboardHelper: https://gist.github.com/JasonCanCode/78006e7bf5c670376eda5d7fee0ad6c4