How to access first User in an Array - arrays

Question

I'm trying to download user from Firebase and save them in an array using a Usermodel.
The download works so far, but how do I access the first user and show the picture of this user?
My Usermodel: Sorry for some German words
class UserModel {
var username: String?
var email: String?
var profilImageUrl: String
var birthdayDate: String?
var gender: String?
var userDescription: String?
init(dictionary: [String: Any]) {
username = dictionary["username"] as? String
email = dictionary["email"] as? String
profilImageUrl = dictionary["profilImageURL"] as? String ?? ""
birthdayDate = dictionary["Geburtsdatum"] as? String
gender = dictionary["gender"] as? String
userDescription = dictionary["description"] as? String
}
In the following I´m saving the downloaded Data to the array "attendees".The picture of the first user in this array should be shown in firstUserImageView.
import SDWebImage
var attendees = [UserModel]()
#IBOutlet weak var firstUserImageView: UIImageView!
//load attendees with Api -> that works.
print(attendees.count) gives me the amount of attendees saved in the database
func loadAttendees(){
guard let eventID = event?.id else {return}
AttendeeApi.shared.observeEventAttendee(eventID: eventID) { (attendeeId) in
AttendeeApi.shared.observeAttendee(attendeeId: attendeeId, completion: { (attendee) in
self.attendees.append(attendee)
})
}
}
Set up the image view
var attendee: UserModel?{
didSet {
let firstAttendee = attendees[0].profilImageUrl
guard let firstUserImageUrl = URL(string: firstAttendee) else {return}
firstUserImageView.sd_setImage(with: firstUserImageUrl) { (_, _, _, _) in
}
}
}
loadAttendees is called in viewDidLoad but the ImageView does not show the picture of the first user.
var REF_ATTENDEE = Database.database().reference().child("users")
func observeAttendee (attendeeId: String, completion: #escaping (UserModel) -> Void) {
REF_ATTENDEE.child(attendeeId).observeSingleEvent(of: .value) { (snapshot) in
guard let dic = snapshot.value as? [String: Any] else {return}
let newAttendee = UserModel(dictionary: dic)
completion(newAttendee)
}
}
var REF_EVENTS_ATTENDEES = Database.database().reference().child("events - attendees")
func observeEventAttendee(eventID: String, completion: #escaping (String) -> Void) {
REF_EVENTS_ATTENDEES.child(eventID).observe(.childAdded) { (snapshot) in
let attendeeId = snapshot.key
completion(attendeeId)
}
}