How do I append data from a child item in Firebase database?

Question

How do I append data from a child item in Firebase database? Below is my code.

import UIKit
import Firebase
import FirebaseDatabase

class MedalViewController: UICollectionViewController {

    var imagesArray = [String]()
    var identities = [String]()
    var identities2 = [String]() //Creates an empty array 
    var imagesArrayGreyed = [String]()
    let databaseRef = FIRDatabase.database().reference()
    let userID = FIRAuth.auth()?.currentUser?.uid

    override func viewDidLoad() {
        super.viewDidLoad()
        imagesArray = ["1", "2", "3"] //Add all the medal images here
        identities = ["Shield", "Tie", "Star"] //Add all the identities here
        identities2 = ["Shield"] //Choose what medals the user has.
        imagesArrayGreyed = ["1Greyed","2Greyed","3Greyed"] //Add all the greyed images here

        databaseRef.child("users").child(userID!).observeSingleEventOfType(.Value, withBlock: { (snapshot) in
            // Get user value
            var newIdentities2 = snapshot.value!["medals"] as! String

            // how do I continue on from here?


            // ...
        }) { (error) in
            print(error.localizedDescription)
        }


    }

Here's a picture of my Firebase data structure:

Data should only be obtained once when the ViewController is opened and then appended into the array. Thanks for your help.

Edit: The intention is to obtain data from the firebase child 'medals' and append it to the local array "identifier2"

Answer 1

databaseRef.child("users").child(userID!).observeSingleEventOfType(.Value, withBlock: { (snapshot) in
        // Get user value
        if let identities = snapshot.value! as? [String:AnyObject]{
                for each in identities.1 as String{
                   identifier2.append(each)//will append medals
                }
        }
        // ...
    }) { (error) in
        print(error.localizedDescription)
    }