Updating array within map within array in Firestore database (Swift)

Question

struct Game: Codable {
    
    let id: String
    
    var table = Table()
    
    var players = [Player]()
    
    var player1ID = ""
    var player2ID = ""
    
    var currentPlayerSetCountShouldAnimate = false
    var opponentSetCountShouldAnimate = false
    
    init(currentPlayer: Player) {
        id = UUID().uuidString
        players.append(currentPlayer)
        players[0].playerNumber = 0
        player1ID = currentPlayer.id
    }
}

struct Player: Codable, Equatable {
    var id = UUID().uuidString
    
    var playerNumber = 0
    
    var selectedCards: [Card]
    var collectedSets: [Card]
    var selectedCardsIndexes: [Int]
    
}

I'm storing the Game object in a Firestore database. Rather than updating the entire game when a Card object is added to the selectedCards array, I want to update only the selectedCards array for the currentPlayer.

func updatePlayerSelectedCards(player: Player) {
    do {
        let selectedCards = try JSONEncoder().encode(player.selectedCards)
        let gameRef = Firestore.firestore().collection("Game").document(game.id)
        let playerRef = gameRef.collection("players")

        playerRef.document("\(player.playerNumber)").updateData(["selectedCards": selectedCards]) { (error) in
            if let error = error {
                print("Error updating selectedCards field: \(error)")
            } else {
                print("Successfully updated selectedCards field")
            }
        }
    } catch {
        print(error.localizedDescription)
    }
}

I've written a number of variations on this function, but when I try to access the playerNumber index of the players array, it gives me this error:

[FirebaseFirestore][I-FST000001] WriteStream (7f9b27810c08) Stream error: 'Not found: No document to update: projects/setgamebc/databases/(default)/documents/Game/FC600D8C-85DC-4465-8648-31FFA90086EB/players/0'

In the attached image, it's clear that the index (0 in this case) exists in the player array. Is it not a document? Do I need to use FieldValue.arrayUnion for this? This is my first "large" project, and I feel like accomplishing this shouldn't be that hard, so I think I may be missing something simple. Any help and clarification would be greatly appreciated.

Answer 1

The problem starts here:

let playerRef = gameRef.collection("players")
playerRef.document("\(player.playerNumber)")...

This code tries to update a $player.playerNumber document in a players collection . But your screenshot shows a players field in an otherwise named document. So there is no document called players , which explains the error message.

There is no way operator to update an item in an array field in Firestore; the only operators are to add a unique item, remove specific items , or to set the entire field.

So if the array_union operator is not good enough for your use-case, you'll have to: 1) read the array, 2) update it in your application code, 3) write the entire array back to the database.

Also see: Firestore Update single item in array of objects