How to reload UITableView from different controller - ios

Question

I am attempting to make a to-do app with a controller for both "this week" and "next week." (Objects with a date in the current week will be shown in the thisWeek view controller, while objects with a date next week will be shown in the nextWeek view controller. However, sometimes objects will not appear in the table until the app restarts, and I'm not sure why this is happening or how to fix it.
My theory is that each table in the different controllers needs to be reloaded each time data is added/changed. I just don't know how to access the table from a different controller than the one I am in.
Attempt 1 I tried to use a singleton that looked like this:
class ToDoTables {
private init() {}
static let shared = ToDoTables()
lazy var thisTable: UITableView = {
let thisWeek = UITableView()
return thisWeek
}()
lazy var nextTable: UITableView = {
let nextWeek = UITableView()
return nextWeek
}()
}
then to be called like:
let thisTable = ToDoTables.shared.thisTable
However this did not work because I initially created the table using storyboard and just used an IBOutlet in the controller, and couldn't find way to keep the outlet and also use singleton. Next, I tried to remove the outlet and just use the code above. When I simulated the app, it crashed because the outlet couldn't be found or something like that (which was expected).
Attempt 2
I tried to access the other controller's table by creating an instance of the vc and accessing the table that way:
NextWeekController().nextTable.reloadData()
but got an error that said "Unexpectedly found nil while implicitly unwrapping an Optional value"
So I'm not sure if that is my tables need to be reloaded each time, or if it is something else.
Overview of non-functioning operations (an app restart is needed, or the controller/table needs loaded again):
something created in the nextWeek controller with a date in the current week will not appear
when an object in created in nextWeek controller, then date is changed from next week to this week
something created in the thisWeek controller with a date in the next week will not appear
when an object in created in thisWeek controller, then date is changed from this week to next week

Answer 1

My theory is that each table in the different controllers needs to be reloaded each time data is added/changed.
You are correct. For UITableView.reloadData(), the Apple Docs state to:
Call this method to reload all the data that is used to construct the
table
In other words, it is necessary to reload the table view's data with this method if the data is changed.
I just don't know how to access the table from a different controller
than the one I am in.
One solution is to create global references to all your view controllers through one shared instance.
// GlobalVCs.swift
class GlobalVCs {
static var shared = GlobalVCs()
var nameOfVC1!
var nameOfVC2!
var nameOfVC3!
// and so on
private init() {}
}
Then set the global vc references from each view controller's viewDidLoad() method.
Example:
// VC1.swift
override func viewDidLoad() {
GlobalVCs.shared.vc1 = self
}
Then you can access a view controller anywhere with GlobalVCs.shared.vc1, GlobalVCs.shared.vc2, etc.

Answer 2

Sorry, but need to say that this is wrong approach. We need to follow to MCV model where we have data model, view and controller. If you example for to-do model you could have:
import Foundation
import FirebaseFirestore
import FirebaseFirestoreSwift
struct ToDoItem: Codable, Identifiable {
static let collection = "todos"
#DocumentID var id: String?
var uid: String;
var done: Bool;
var timestamp: Timestamp;
var description: String
}
Then you need to have repository for this type of data, for example if we are using Firebase we can have
import Foundation
import Combine
import FirebaseFirestore
import FirebaseFirestoreSwift
class BaseRepository<T> {
#Published var items = Array<T>()
func add(_ item: T) { fatalError("This method must be overridden") }
func remove(_ item: T) { fatalError("This method must be overridden") }
func update(_ item: T) { fatalError("This method must be overridden") }
}
and then we have ToDoRepository (singleton object)
import Foundation
import FirebaseFirestore
import FirebaseFirestoreSwift
import Resolver
import CoreLocation
import Combine
class ToDoRepository: BaseRepository<ToDoItem>, ObservableObject {
var db = Firestore.firestore()
uid: String? {
didSet {
load()
}
}
private func load() {
db.collection(ToDoItem.collection).whereField("uid", isEqualTo: uid).order(by: "timestamp").addSnapshotListener {
( querySnapshot, error ) in
if let querySnapshot = querySnapshot {
self.items = querySnapshot.documents.compactMap { document -> ToDoItem? in
try? document.data(as: ToDoItem.self)
}
}
}
}
}
Now we need to register repository in AppDelegate+Injection.swift:
import Foundation
import Resolver
extension Resolver: ResolverRegistering {
public static func registerAllServices() {
// Services
register { ToDoRepository() }.scope(application)
}
}
After that we can use ToDoRepository in any controller :
import UIKit
import Combine
import Resolver
class MyController: UIViewController {
private var cancellables = Set<AnyCancellable>()
#LazyInjected var toDoRepository: ToDoRepository
// and listen and update any table view like this
override func viewDidLoad() {
super.viewDidLoad()
toDoRepository.$items
.receive(on: DispatchQueue.main)
.sink { [weak self] todos
self?.todos = todos
tableView.reloadData()
}
.store(in: &cancellables)
}
}