MenuBuilder

menuBuilder.swift

class MenuBuilder {
    var menu = [MenuItem]()
    
    @discardableResult
    func separator() -> Self {
        menu.append(MenuItemSeparator()) // a different type of cell, contains a separator.
        return self
    }
    
    @discardableResult
    func items(_ items: MenuItemModel...) -> Self {
        menu.append(contentsOf: items)
        return self
    }
    
    @discardableResult
    func item(iconNamed: String?, title: String, instance: ViewControllerConvertable) -> Self {
        let item = MenuItemModel(
            icon: iconNamed != nil ? UIImage(named: iconNamed!)?.withRenderingMode(.alwaysTemplate) : nil,
            title: title,
            instance: instance
        )
        menu.append(item)
        return self
    }
    
    @discardableResult
    func item(iconImage: UIImage?, title: String, instance: ViewControllerConvertable) -> Self {
        let item = MenuItemModel(
            icon: iconImage?.withRenderingMode(.alwaysTemplate),
            title: title,
            instance: instance
        )
        menu.append(item)
        return self
    }

}

MenuItem.swift

protocol MenuItem { }

struct MenuItemSeparator: MenuItem { }

struct MenuItemModel: MenuItem {
    let icon: UIImage?
    let title: String
//    var instance: Instantiatable.Type
    fileprivate var instance: ViewControllerConvertable
    
    var viewController: UIViewController {
        instance.viewController
    }
}

MenuViewController.swift

class MenuViewController: UIViewController, Instantiatable {
  @IBOutlet weak var tableView: UITableView!
  
  var onSelectItem: ((MenuItemModel) -> Void)?
    
    private var items = [MenuItem]() {
        didSet { tableView.reloadData() }
    }
  
  private func buildMenu() {
    let builder = MenuBuilder()
    builder
      .item(iconNamed: "first", title: "First Menu", instance: ViewControllerInstantiator(FirstMenuViewController.self))
      .separator()
    
    // OR
    builder.item(iconNamed: "menu-survey", title: "Survey", instance: ViewControllerInitialized {
            let viewModel = SurveyListViewModel()
            let sample = SurveyListViewController(viewModel: viewModel)
            return sample
    })
    
    // Generate menu items.
    items = builder.menu
  }
}

// MARK: - Delegate, Datasource.

extension MenuViewController: UITableViewDelegate, UITableViewDataSource {
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        items.count
    }
    
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let item = items[indexPath.row]
        switch item {
        case _ as MenuItemSeparator:
            let cell: MenuItemSeparatorTableViewCell = tableView.reusableCell(for: indexPath)
            return cell
            
        case let item as MenuItemModel:
            let cell: MenuItemTableViewCell = tableView.reusableCell(for: indexPath)
            cell.configure(item)
            return cell
            
        default: fatalError()
        }
    }
    
    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        let item = items[indexPath.row]
        guard let menuItem = item as? MenuItemModel else { return }
        onSelectItem?(menuItem)
    }
}

ViewControllerConvertable.swift

protocol ViewControllerConvertable {
    var viewController: UIViewController { get }
}

struct ViewControllerInstantiator: ViewControllerConvertable {
    
    let instantiatableType: Instantiatable.Type // Refer: https://gist.github.com/lalkrishna/3770ce3933feaf4d7c0d3f1323e7fd72
    
    internal init(_ instantiatableType: Instantiatable.Type) {
        self.instantiatableType = instantiatableType
    }
    
    var viewController: UIViewController {
        instantiatableType.instantiate() as! UIViewController // swiftlint:disable:this force_cast
    }
}

struct ViewControllerInitialized: ViewControllerConvertable {
    
    private let `internal`: () -> UIViewController
    
    internal init(_ internal: @escaping () -> UIViewController) {
        self.internal = `internal`
    }
    
    var viewController: UIViewController {
        `internal`()
    }
}