Unpacking Firestore array with objects to a model in swift

Question

I have a project in swift with Firestore for the database. My firestore dataset of a user looks like this. User details with an array that contains objects.

I have a function that gets the specifick user with all firestore data:

func fetchUser(){
    
    db.collection("users").document(currentUser!.uid)
        .getDocument { (snapshot, error ) in
            do {
                if let document = snapshot {
                    
                    let id = document.documentID
                    let firstName = document.get("firstName") as? String ?? ""
                    let secondName = document.get("secondName") as? String ?? ""
                    let imageUrl = document.get("imageUrl") as? String ?? ""
                    let joinedDate = document.get("joinedDate") as? String ?? ""
                    let coins = document.get("coins") as? Int ?? 0
                    let challenges = document.get("activeChallenges") as? [Challenge] ?? []
                    
                    let imageLink = URL(string: imageUrl)
                    
                    let imageData = try? Data(contentsOf: imageLink!)
                    
                    let image = UIImage(data: imageData!) as UIImage?
                    
                    let arrayWithNoOptionals = document.get("activeChallenges").flatMap { $0 }
                    print("array without opt", arrayWithNoOptionals)
                    
                    self.user = Account(id: id, firstName: firstName, secondName: secondName, email: "", password: "", profileImage: image ?? UIImage(), joinedDate: joinedDate, coins: coins, activeChallenges: challenges)
                }
                else {
                    print("Document does not exist")
                    
                }
            }
            catch {
                fatalError()
            }
        }
}

This is what the user model looks like:

class Account {
var id: String?
var firstName: String?
var secondName: String?
var email: String?
var password: String?
var profileImage: UIImage?
var coins: Int?
var joinedDate: String?
var activeChallenges: [Challenge]?


init(id: String, firstName: String,secondName: String, email: String, password: String, profileImage: UIImage, joinedDate: String, coins: Int, activeChallenges: [Challenge]) {
    self.id = id
    self.firstName = firstName
    self.secondName = secondName
    self.email = email
    self.password = password
    self.profileImage = profileImage
    self.joinedDate = joinedDate
    self.coins = coins
    self.activeChallenges = activeChallenges
}

init() {
    
}

}

The problem is I don't understand how to map the activeChallenges from firestore to the array of the model. When I try : let challenges = document.get("activeChallenges") as? [Challenge] ?? [] The print contains an empty array, but when i do: let arrayWithNoOptionals = document.get("activeChallenges").flatMap { $0 } print("array without opt", arrayWithNoOptionals)

This is the output of the flatmap: it returns an optional array

You can’t cast to [Challenge], you need to use .map.

Joakim Danielson
– Joakim Danielson

2021-05-16 16:14:33 +00:00
Commented May 16, 2021 at 16:14 — Joakim Danielson
– Joakim Danielson, Commented May 16, 2021 at 16:14

Hai Pham · Accepted Answer · 2021-05-16 16:57:40Z

3

System can not know that activeChallenges is array of Challenge object. So, you need to cast it to key-value type (Dictionary) first, then map it to Challenge object

let challengesDict = document.get("activeChallenges") as? [Dictionary<String: Any>] ?? [[:]]
let challenges = challengesDict.map { challengeDict in
    let challenge = Challenge()
    challenge.challengeId = challengeDict["challengeId"] as? String
    ...
    return challenge
}

This is the same way that you cast snapshot(document) to Account object

answered May 16, 2021 at 16:57

Hai Pham

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