Firestore - Subcollections Swift - swift

Question

So I'm trying to learn some Firestore basic functionality and have watched "Kilo Locos" videos on YouTube explaining CRUD operations. I want to take his method of code and create subcollections from it. Basically, how can I add a collection and make the 'User' collection a sub collection from this new collection. Any help is greatly appreciated, many thanks!!
Here is a link to download the project:
https://kiloloco.com/courses/youtube/lectures/3944217
FireStore Service
import Foundation
import Firebase
import FirebaseFirestore
class FIRFirestoreService {
private init() {}
static let shared = FIRFirestoreService()
func configure() {
FirebaseApp.configure()
}
private func reference(to collectionReference: FIRCollectionReference) -> CollectionReference {
return Firestore.firestore().collection(collectionReference.rawValue)
}
func create<T: Encodable>(for encodableObject: T, in collectionReference: FIRCollectionReference) {
do {
let json = try encodableObject.toJson(excluding: ["id"])
reference(to: collectionReference).addDocument(data: json)
} catch {
print(error)
}
}
func read<T: Decodable>(from collectionReference: FIRCollectionReference, returning objectType: T.Type, completion: #escaping ([T]) -> Void) {
reference(to: collectionReference).addSnapshotListener { (snapshot, _) in
guard let snapshot = snapshot else { return }
do {
var objects = [T]()
for document in snapshot.documents {
let object = try document.decode(as: objectType.self)
objects.append(object)
}
completion(objects)
} catch {
print(error)
}
}
}
func update<T: Encodable & Identifiable>(for encodableObject: T, in collectionReference: FIRCollectionReference) {
do {
let json = try encodableObject.toJson(excluding: ["id"])
guard let id = encodableObject.id else { throw MyError.encodingError }
reference(to: collectionReference).document(id).setData(json)
} catch {
print(error)
}
}
func delete<T: Identifiable>(_ identifiableObject: T, in collectionReference: FIRCollectionReference) {
do {
guard let id = identifiableObject.id else { throw MyError.encodingError }
reference(to: collectionReference).document(id).delete()
} catch {
print(error)
}
}
}
FIRCollectionReference
import Foundation
enum FIRCollectionReference: String {
case users
}
User
import Foundation
protocol Identifiable {
var id: String? { get set }
}
struct User: Codable, Identifiable {
var id: String? = nil
let name: String
let details: String
init(name: String, details: String) {
self.name = name
self.details = details
}
}
Encodable Extensions
import Foundation
enum MyError: Error {
case encodingError
}
extension Encodable {
func toJson(excluding keys: [String] = [String]()) throws -> [String: Any] {
let objectData = try JSONEncoder().encode(self)
let jsonObject = try JSONSerialization.jsonObject(with: objectData, options: [])
guard var json = jsonObject as? [String: Any] else { throw MyError.encodingError }
for key in keys {
json[key] = nil
}
return json
}
}
Snapshot Extensions
import Foundation
import FirebaseFirestore
extension DocumentSnapshot {
func decode<T: Decodable>(as objectType: T.Type, includingId: Bool = true) throws -> T {
var documentJson = data()
if includingId {
documentJson!["id"] = documentID
}
let documentData = try JSONSerialization.data(withJSONObject: documentJson!, options: [])
let decodedObject = try JSONDecoder().decode(objectType, from: documentData)
return decodedObject
}
}

Answer 1

The Firestore structure cannot have collection as children of other collections.
The answer to your question (How can I add a collection and make the 'User' collection a sub collection from this new collection?) is you cannot. Instead you must put a document between those two collections.
Read this for more information.
It says: Notice the alternating pattern of collections and documents. Your collections and documents must always follow this pattern. You cannot reference a collection in a collection or a document in a document.