problem with adding element to swift array - swift

Question

I am creating an application. I make a request to the firebase store, after that I add the result to the array, but in the end, when the array is displayed from viewDidLoad or other functions, I get an empty array. But if you make a conclusion immediately after the request, then everything is displayed correctly
`
import UIKit
import Firebase
import FirebaseStorage
import FirebaseFirestore
class CatalogVC: UIViewController {
struct Item: Codable {
var title: String
var price: Int
var description: String
var imageUrl: String
}
#Published var items: [Item] = []
let database = Firestore.firestore()
#IBOutlet weak var textViewCatalog: UITextView!
override func viewDidLoad() {
super.viewDidLoad()
let settings = FirestoreSettings()
Firestore.firestore().settings = settings
itemsList()
print(items)
showCatalogVC()
}
#IBAction func showCatalogTapped() {
}
private func showCatalogVC() {
print("SHOW CATALOG")
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let dvc = storyboard.instantiateViewController(withIdentifier: "CatalogVC") as! CatalogVC
self.present(dvc, animated: true, completion: nil)
}
func itemsList(){
database.collection("catalog")
.getDocuments { (snapshot, error) in
self.items.removeAll()
if let snapshot {
for document in snapshot.documents{
let docData = document.data()
let title: String = docData["title"] as? String ?? ""
let imageUrl: String = docData["imageUrl"] as? String ?? ""
let description: String = docData["description"] as? String ?? ""
let price: Int = docData["price"] as? Int ?? 0
let item: Item = Item(title: title, price: price, description: description, imageUrl: imageUrl)
self.items.append(item)
}
}
}
}
}
`
I am creating an application. I make a request to the firebase store, after that I add the result to the array, but in the end, when the array is displayed from viewDidLoad or other functions, I get an empty array. But if you make a conclusion immediately after the request, then everything is displayed correctly

Answer 1

Getting data from Firebase is asynchronous process. So here you should make everything after loading data in closure database.collection("catalog").getDocuments {...}.
func itemsList(){
database.collection("catalog")
.getDocuments { (snapshot, error) in
self.items.removeAll()
if let snapshot {
for document in snapshot.documents{
let docData = document.data()
let title: String = docData["title"] as? String ?? ""
let imageUrl: String = docData["imageUrl"] as? String ?? ""
let description: String = docData["description"] as? String ?? ""
let price: Int = docData["price"] as? Int ?? 0
let item: Item = Item(title: title, price: price, description: description, imageUrl: imageUrl)
self.items.append(item)
}
}
print(self.items) //print items to see them
//here use items data
}
}