write (add) multiple array in firestore - swift

Question

I try to add multiple array in firestore using struct codable in swiftui but when I add, it updates the same array added but i want add more array in my list...
as you can see in the image, every time I add a text, it updates my index "0" but I want to add multiple indexes, for example O, 1, 2... in my array" tags"
ViewModel
class DataManager: ObservableObject {
#Published var books = Book(tags: [Tag(title: "", color: "")])
func addBookNew(nom: String, prenom: String){
//guard let userID = Auth.auth().currentUser?.uid else {return}
let db = Firestore.firestore()
let collectionRef = db.collection("Users").document("TEST")
do {
let data = Book(tags: [Tag(title: nom, color: prenom)])
try collectionRef.setData(from: data)
}
catch {
print(error)
}
}
STRUCT BOOK
import Foundation
import FirebaseFirestore
import FirebaseFirestoreSwift
struct Book: Codable {
#DocumentID var id: String?
let tags: [Tag]
}
STRUCT TAG
import Foundation
import FirebaseFirestoreSwift
struct Tag: Codable, Hashable {
let title: String
let color: String
}
LIST VIEW
import SwiftUI
import Firebase
struct ListView: View {
#StateObject var dataManager = DataManager()
#State private var showPopUp = false
#EnvironmentObject var viewModel: AppViewModel
var books: [Book]
#State var nomTF = ""
#State var prenomTF = ""
#State var dismiss = false
var body: some View {
NavigationView{
VStack{
TextField("nom", text: $nomTF )
TextField("prenom", text: $prenomTF)
Button("save") {
dataManager.addBookNew(nom: nomTF, prenom: prenomTF)
}
List{
ForEach(dataManager.books.tags, id: \.self) { book in
HStack{
Text("T: \(book.title)")
Text("C: \(book.color)")
}
}
}
}.onAppear(){
dataManager.fetchtest()
}

Answer 1

The problem is here:
let data = Book(tags: [Tag(title: nom, color: prenom)])
try collectionRef.setData(from: data)
This code tells Firestore to set the tags field to the array that you specify in the call.
If you want to add unique items to existing array, you can use FieldValue.arrayUnion([...]).
let data = Book(tags: FieldValue.arrayUnion([Tag(title: nom, color: prenom)]))
try collectionRef.setData(from: data)
Note that this will only add the item if it is not already in the array. If you want to allow for duplicate items, you will have to read the array from the document first, then updates in your application code, and finally write the entire array back to the database.
Update: it seems your Book class can only accept Tag in its tags field, so you can't specify an FieldValue.arrayUnion there. It's probably easiest to then simply perform the union in the database call:
try collectionRef.updateData([
"tags": FieldValue.arrayUnion([Tag(title: nom, color: prenom)])
])
So instead of writing the entire book here, we're updating a single field in the document, and in there perform the array union.
washingtonRef.updateData([
"regions": FieldValue.arrayUnion(["greater_virginia"])
])