Update tabbarcontroller badge from a static struct - ios

Question

I'm not sure if this is possible or if I'm going about this the wrong way but...
I have an ecommerce app. You can add products to your cart. I'd like to display a badge over cart with the item quantity in the cart.
However, my Cart is in a static struct which needs to update the tabbarController.
How can I get these two to communicate between each other?
Cart
import Foundation
struct Cart {
static var items: [CartItem] = []
static func updateItem(id:Int,increment:Int){
var itemAdded = false
for (index, item) in items.enumerated() {
if item.fabric.id == id {
item.quantity = item.quantity+increment
if item.quantity <= 0 {
items.remove(at: index)
}
itemAdded = true
}
}
if !itemAdded {
// fabric not in cart
// add it
for item in API.fabrics{
if item.id == id{
items.append(CartItem(fabric: item, quantity: 1))
return
}
}
}
// AREA IN QUESTION
// let MainTabBarController = AppDelegate
// if let tabItems = tabBarController?.tabBar.items{
//
// }
}
}
class CartItem{
let fabric: Fabric
var quantity: Int
init(fabric: Fabric,
quantity: Int){
self.fabric = fabric
self.quantity = quantity
}
}
app delegate
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
// Override point for customization after application launch.
UIApplication.shared.statusBarStyle = .lightContent
window = UIWindow(frame: UIScreen.main.bounds)
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let MainTabBarController = storyboard.instantiateViewController(withIdentifier: "MainTabBarController")
window?.rootViewController = MainTabBarController
window?.makeKeyAndVisible()
return true
}

Answer 1

You can use NSNotificationcenter.post(_ notification: Notification), so everytime you add an item to your cart you post a notification, and the your TabController can subscribe to this notification and handle it. Something like:
import NotificationCenter
import UIKit
struct Cart {
func add(item: Int) {
// Your code to handle stuff...
let numberOfItems = item
let notification = Notification(name: Notification.Name(rawValue: "addItem"), object: nil, userInfo: ["numberOfItems":numberOfItems])
NotificationCenter.default.post(notification)
}
}
class YourTabBarController: UITabBarController {
override func viewDidLoad() {
NotificationCenter.default.addObserver(self, selector: #selector(handleAddItem), name: NSNotification.Name(rawValue: "addItem"), object: nil)
}
#objc func handleAddItem(notification: Notification) {
// increment badge value
tabBar.items?.first?.badgeValue = "\(notification.userInfo!["numberOfItems"]!)"
}
}
Of course, you can do the same thing to remove items and every other stuff you need.

Answer 2

If tabbarcontroller is the rootviewcontroller
if let tabbarController = UIApplication.shared.keyWindow?.rootViewController as? MainTabBarController{
tabbarControllertabBar.items[indexpOfTabbarItem]!.badgeValue = value
}
if rootviewcontroller is navigationcontroller of tabbarcontroller:
if let tabbarNavigationController = UIApplication.shared.keyWindow?.rootViewController as? UINavigationController, let tabbarController = tabbarNavigationController.viewControllers.first as? MainTabBarController {
tabbarControllertabBar.items[indexpOfTabbarItem]!.badgeValue = value
}