Unable to Fetch Users Firebase Firestore - swift

Question

Unable to fetch list of users from firebase. print returns as [] . Code is below. Any help would be awesome!
let COLLECTION_USERS = Firestore.firestore().collection("users")
func fetchUsers() {
COLLECTION_USERS.getDocuments { snapshot, _ in
guard let documents = snapshot?.documents else {return}
self.users = documents.compactMap({try? $0.data(as: User.self)})
print(self.users)
}
I expect the 7 users that I have signed up to print that data.

Answer 1

If documents.count shows that you've got 7 documents, but self.users contains no elements after running the mapping, this indicates your Firestore documents can't be mapped to your Swift structs.
Please make sure that the data types on your Swift structs match the types used in your Firestore documents.
You should also use code that is more error-resilient. In your code, you explicitly drop the error parameter on the closure - you rather don't want to do this.
The following code snippet (taken from the official docs) shows how to do this.
let docRef = db.collection("cities").document("BJ")
docRef.getDocument { (document, error) in
// Construct a Result type to encapsulate deserialization errors or
// successful deserialization. Note that if there is no error thrown
// the value may still be `nil`, indicating a successful deserialization
// of a value that does not exist.
//
// There are thus three cases to handle, which Swift lets us describe
// nicely with built-in Result types:
//
// Result
// /\
// Error Optional<City>
// /\
// Nil City
let result = Result {
try document?.data(as: City.self)
}
switch result {
case .success(let city):
if let city = city {
// A `City` value was successfully initialized from the DocumentSnapshot.
print("City: \(city)")
} else {
// A nil value was successfully initialized from the DocumentSnapshot,
// or the DocumentSnapshot was nil.
print("Document does not exist")
}
case .failure(let error):
// A `City` value could not be initialized from the DocumentSnapshot.
print("Error decoding city: \(error)")
}
}