Xtykutl

I want to understand why using a struct is causing this issue and a class does not. I encountered the issue when appending elements to array and having an observer load a table. Here are the codes:

Order.swift - items ordered

struct Order {

    var menuItems: [MenuItem]

    init(menuItems: [MenuItem] = ) {

        self.menuItems = menuItems

    }

}

MenuController.swift - contains the order and a shared instance

struct MenuController {  

    static var shared: MenuController = MenuController()

    static let orderNotification = Notification.Name("MenuController.orderUpdated")



    var order = Order() {

        didSet {

            NotificationCenter.default.post(name: MenuController.orderNotification,

                                            object: nil)

    }

}

MenuItemViewController.swift - ordering screen

@IBAction func orderButtonTapped(_ sender: UIButton) {

     MenuController.shared.order.menuItems.append(menuItem)

 }

OrderTableViewController.swift - items ordered screen

override func viewDidLoad() {

    super.viewDidLoad()



    NotificationCenter.default.addObserver(tableView, 

                      selector: #selector(UITableView.reloadData),

                      name: MenuController.orderNotification, object: nil)

}

...

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {

    return MenuController.shared.order.menuItems.count //Simultaneous access error thrown here

}

Now, I made a design mistake where MenuController should be a class instead of a struct because we're gonna be sharing MenuController instance throughout the app hence it should be a reference type. Using a class solved the simultaneous access issue.

What I am confused about is :
Why is a value-typed (struct) MenuController causing this simultaneous access issue when observer try to load the tableView.

Hope someone can explain. TIA!