How to store values ​​received asynchronously in a global array?

Question

Swift

I am getting data from Firebase and I want to store it in an array of structures ( PostData ) so that I can populate the CollectionViewCell cells inside the TableViewCell through it. The problem is that I get the data, at some point I even manage to calculate it, but to just store it in an array and use it between classes - no chance :( Here is the code of the table where I want to receive data (Social.swift) :

var dataPosts = [PostData]()

 override func viewDidLoad() {
        super.viewDidLoad()
        tableView = UITableView(frame: self.view.bounds, style: .grouped)
        tableView.delegate = self
        tableView.dataSource = self
        ...
        self.parsePosts() { tempData in
            self.dataPosts = tempData
            self.tableView.reloadData()
          }
    }
...
func parsePosts(completion: @escaping ([PostData]) -> Void) {
        var tempData = [PostData]()
        let databaseRef = Database.database().reference(withPath: "Посты")
        databaseRef.observe(.value) { (snapshot, error) in
            for child in snapshot.children {
                let snap = child as! DataSnapshot
                let res = snap.value as! [String: Any]
                
                let title = res["Заголовок"] as! String
                let subtitle = res["Подзаголовок"] as! String
                let img = res["URL"] as! String
                let date = res["Дата"] as! String
                
                tempData.append(PostData(title: title, subtitle: subtitle, imgURL: img, date: date))
                
            }
            DispatchGroup().notify(queue: .main) {
                self.tableView.reloadData()
                let postCell = PostCell()
                postCell.dataForPosts = tempData
                print(postCell.dataForPosts, "в старом классе" ) // Выводит, что нужно
            }
            completion(tempData)
        }
    }

And here is the TableViewCell code ( PostCell.swift ), where the number of elements of the dataForPosts array is zero, although if called with Social.swift, then everything is fine:

var dataForPosts:[PostData] = []
...
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: self.PostCollectionID, for: indexPath)
        print(self.dataForPosts, " - в другом классе ") // Выводит пустой массив
        cell.layer.borderWidth = 5
        cell.layer.cornerRadius = 20
        
        return cell
    }

How can this problem be solved? Thanks

Answer 1

If it’s very clumsy and primitive and practically never do it, then make Social a singleton and refer to it, and not to self, in print(self.dataForPosts, "- in another class "
) datasource for the table at the moment of initiating the datasource and then refer to the instance of the Social class already stored in the property. ... specify, ask, I can imagine how what I just wrote is seen from the outside, but now I don’t understand how to write otherwise.