Array is updating before variables are updated in Swift - ios

Question

I'm trying to get list of toys from Firestore and put it into array
But when I call function, it returns empty array, and just after returning it prints Toy object, so order is broken.
I thought that closures would help me, but I think I don't know how to use them, and examples from Google don't help me
Here is my code (I use SwiftUI so I created swift file with variable)
let db = Firestore.firestore()
class DataLoade {
func loadFirebase(completionHandler: #escaping (_ toys: [Toy]) -> ()){
var toysar: [Toy] = []
let toysRef = db.collection("Toys")
toysRef.getDocuments() { (querySnapshot, err) in
if let err = err {
print("Error getting documents: \(err)")
} else {
for document in querySnapshot!.documents {
var name: String = document.get("name") as! String
var id: Int = document.get("id") as! Int
var description: String = document.get("description") as! String
var imageName: String = document.get("imageName") as! String
var price: String = document.get("price") as! String
var category: String = document.get("category") as! String
var timeToy = Toy(id: id, name: name, imageName: imageName, category: category, description: description, price: price)
toysar.append(timeToy)
}
}
}
completionHandler(toysar)
// print(toysar)
}
}
that's what it prints out:
[] // it prints empty array, but it is in the end of the code
Toy(id: 1001, name: "Pikachu", imageName: "pikachu-plush", category: "lol", description: "kek", price: "350₽") // and now it prints Toy object, however it is in the start of the code
Ok, so I tried to make completion handler for my function, like in "duplicated" answer, but that doesn't work: array is returning before completion handler works
ContentView.swift
func updateArray() -> [Toy]{
dl.loadFirebase() { toys in
ll = toys
}
print("lol \(datas)") // prints «lol []»
return ll
}

Answer 1

You can wait for an asynchronous task using a DispatchGroup. But the trick is NOT to associate asynchronous tasks with return statements. Instead, use closures to do an action after the task is done.
Disclaimer: I wrote this on SO, I apologize in advance for syntax issues.
let toyData = loadFirebase( { (toys) in
print(toys)
//Do something with toys when done
//You could add another completionHandler incase it fails.
//So 1 for pass and 1 for fail and maybe another for cancel. W/e u want
} )
let db = Firestore.firestore()
func loadFirebase(completionHandler:#escaping ((toys: [Toy]?) -> Void)) {
//Create Group
let downloadGroup = DispatchGroup()
var toysar: [Toy] = []
let toysRef = db.collection("Toys")
//If you had multiple items and wanted to wait for each, just do an enter on each.
downloadGroup.enter()
toysRef.getDocuments() { (querySnapshot, err) in
if let err = err {
print("Error getting documents: \(err)")
} else {
for document in querySnapshot!.documents {
var name: String = document.get("name") as! String
var id: Int = document.get("id") as! Int
var description: String = document.get("description") as! String
var imageName: String = document.get("imageName") as! String
var price: String = document.get("price") as! String
var category: String = document.get("category") as! String
var timeToy = Toy(id: id, name: name, imageName: imageName, category: category, description: description, price: price)
toysar.append(timeToy)
print(timeToy)
}
//We aren't done until AFTER the for loop, i.e., each item is grabbed.
downloadGroup.leave()
}
}
//Once the queue is empty, we notify the queue we are done
downloadGroup.notify(queue: DispatchQueue.main) {
completionHandler(toys)
}
}
import SwiftUI
var dl = DataLoade()
var ll: [Toy] = []
let semaphore = DispatchSemaphore(value: 1)
struct ContentView: View {
var items: [Toy]
var body: some View {
NavigationView{
ScrollView(){
VStack(alignment: .leading){
ToyRow(category: "Наш выбор", toys: items)
Spacer()
ToyRow(category: "Акции", toys: items)
}
}.navigationBarTitle(Text("Игрушки г.Остров"))}
}
}
func upe(completionHandler:#escaping ((toys: [Toy]?){
dl.loadFirebase(completionHandler: { toy in
ll.append(contentsOf: toy!)
completionHandler(ll)
} )
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
upe(completionHandler: { (toys) in
DispatchQueue.main.async {
ContentView(items: toys)
}
})
}
}