AppKit NSMenu Helper

Menu.swift

import AppKit

public struct MenuHotKeyPress: ExpressibleByStringLiteral {
    public let character: String
    public let modifierKeys: NSEvent.ModifierFlags?
    
    public init(stringLiteral value: String) {
        character = value
        modifierKeys = nil
    }
    
    fileprivate init() {
        character = ""
        modifierKeys = nil
    }
    
    private init(_ character: String, _ modifierKeys: NSEvent.ModifierFlags) {
        self.character = character
        self.modifierKeys = modifierKeys
    }
    
    public static func +(_ lhs: MenuHotKeyPress, _ rhs: NSEvent.ModifierFlags) -> MenuHotKeyPress {
        return MenuHotKeyPress(lhs.character, rhs)
    }
}

public enum NSAppEvent {
    case about
    case hide
    case hideOthers
    case unhideOthers
    case terminate
    
    fileprivate var target: NSApplication {
        return NSApp
    }
    
    fileprivate var selector: Selector {
        switch self {
        case .about:
            return #selector(NSApp.orderFrontStandardAboutPanel(_:))
        case .hide:
            return #selector(NSApp.hide(_:))
        case .hideOthers:
            return #selector(NSApp.hideOtherApplications(_:))
        case .unhideOthers:
            return #selector(NSApp.unhideAllApplications(_:))
        case .terminate:
            return #selector(NSApp.terminate(_:))
        }
    }
    
    fileprivate var keyPress: MenuHotKeyPress {
        switch self {
        case .about: return ""
        case .hide: return "h" + .command
        case .hideOthers: return "h" + [.option, .command]
        case .unhideOthers: return ""
        case .terminate: return "q" + .command
        }
    }
}

public struct MenuItem {
    private let menuItem: NSMenuItem
    
    public var item: NSMenuItem {
        return menuItem
    }
    
    public init(title: String) {
        self.init(title: title, target: nil, action: nil, key: MenuHotKeyPress())
    }
    
    public init(title: String, target: AnyObject?, action: Selector?) {
        self.init(title: title, target: target, action: action, key: MenuHotKeyPress())
    }
    
    public init(title: String, appKitEvent: NSAppEvent) {
        self.init(title: title, target: appKitEvent.target, action: appKitEvent.selector, key: appKitEvent.keyPress)
    }
    
    public init(title: String, target: AnyObject?, action: Selector?, key: MenuHotKeyPress) {
        menuItem = NSMenuItem(title: title, action: action, keyEquivalent: key.character)
        menuItem.target = target
        if let modifier = key.modifierKeys {
            menuItem.keyEquivalentModifierMask = modifier
        }
    }
    
    private init(menuItem: NSMenuItem) {
        self.menuItem = menuItem
    }
    
    public static var separator: MenuItem {
        return MenuItem(menuItem: .separator())
    }
}

public struct MainMenu {
    public let main = NSMenu(title: "Application Menu")
    
    public init(title: String, menuItems: [MenuItem] = []) {
        MainMenu.appendSubmenu(to: main, title: title, menuItems: menuItems)
    }
    
    public func addSubmenu(withTitle title: String, menuItems: [MenuItem]) {
        MainMenu.appendSubmenu(to: main, title: title, menuItems: menuItems)
    }
    
    private static func appendSubmenu(to menu: NSMenu, title: String, menuItems: [MenuItem]) {
        let subMenuItem = menu.addItem(withTitle: title, action: nil, keyEquivalent: "")
        let subMenu = NSMenu(title: title)
        menuItems.forEach { menuItem in
            subMenu.addItem(menuItem.item)
        }
        menu.setSubmenu(subMenu, for: subMenuItem)
    }
}