Grouping an array from firestore in Swift - ios

Question

I have a firestore database that has a number of orders in a restaurant app. I want to group these orders by the table number so as to present the user with a bill/check for each table number.
I have spent a lot of time researching it and I believe I need to using Dictionary and Grouping. As you will see from the code below I have made an attempt which I think might be close.
Here is how my data is structured in firestore:
Here is my bill struct:
import Foundation
struct Bill {
var billID: String
var userID: String
var tableNumber: String
var itemsOrdered: [[String: Any]]
}
And here is my main view controller:
import FirebaseAuth
import FirebaseFirestore
import UIKit
class BillsViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {
#IBOutlet var billTable: UITableView!
var billsArray = [Bill]()
var groupedBills = [[Bill]]()
let db = Firestore.firestore()
func getData() {
let userID = Auth.auth().currentUser!.uid
db.collection("Orders")
.whereField("User_ID", isEqualTo: userID)
.whereField("Order_Complete", isEqualTo: true)
.addSnapshotListener { querySnapshot, error in
if let error = error {
print("Error:\(error.localizedDescription)")
} else {
self.billsArray.removeAll()
for document in querySnapshot!.documents {
let userID = document.get("User_ID") as! String
let tableNumber = document.get("Table_Number") as! String
let docID = document.documentID
let itemsOrdered = document.get("Items_Ordered") as! [[String: Any]]
let bill = Bill(billID: docID, userID: userID, tableNumber: tableNumber, itemsOrdered: itemsOrdered)
self.billsArray.append(bill)
}
}
let groupedDictionaryInFunc = Dictionary(grouping: self.billsArray) { (bill) -> String in
bill.tableNumber
}
print(self.groupedBills)
let keys = groupedDictionaryInFunc.keys.sorted()
print("Keys\(keys)")
keys.forEach {
self.groupedBills.append(groupedDictionaryInFunc[$0]!)
}
}
billTable.reloadData()
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
print("From table func: \(groupedBills)")
return groupedBills[section].count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "billCell", for: indexPath)
let bill = groupedBills[indexPath.section][indexPath.row]
cell.textLabel?.text = "\(bill.itemsOrdered)"
return cell
}
func numberOfSections(in tableView: UITableView) -> Int {
return groupedBills.count
}
override func viewDidLoad() {
super.viewDidLoad()
getData()
billTable.delegate = self
billTable.dataSource = self
}
}
The expected (or desired!) result is it populates my tableview with each section title the table number and then the the contents of the section being the items that were ordered.
Currently I'm getting a blank and my grouped array appears to be empty.
Any help would be appreciated!