UITableview loads data from Firebase and duplicate rows - ios

Question

I am trying to build an app that is loading data from firebase-database.
Saving members to Firebase is working without any problems. Load members from Firebase to my UITableView is working then I am sorting the members and add respectively member under sections header according to first names first letter(A, B, C, etc as seen in iOS contact app) and this is working as well however my problem occur after I have loaded all my users and for example go to Tab 1 and then switch back to Members Tab all displayed members/cells are duplicated. If I repeat the same procedure switching tabs back and forth all cells triplicate and it goes on.
I have searched different sources for a solution but I can not find anything that is similar.
Does anyone know a solution or what I an doing wrong?
Thanks!
My Viewcontroller:
import Foundation
import UIKit
class MembersTableViewController: UITableViewController {
var FBref = FIRDatabaseReference()
var members: [Member] = []
var membersDict = [String: [String]]()
var memberSectionTitles = [String]()
// TODO: Implement user.
//var user: AdminUser!
let fakeuservariable = "fakeuser"
#IBOutlet var memberListTableView: UITableView!
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewDidAppear(_ animated: Bool) {
loadDataFromFirebase()
createFirstnameDict()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
// MARK: - Table view data source
override func numberOfSections(in tableView: UITableView) -> Int {
return memberSectionTitles.count
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
let firstLetterKey = memberSectionTitles[section]
if let firstnameValues = membersDict[firstLetterKey] {
return firstnameValues.count
}
return 0
}
override func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
return memberSectionTitles[section]
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "membercell", for: indexPath)
let firstLetterKey = memberSectionTitles[indexPath.section]
if let firstnameValues = membersDict[firstLetterKey] {
cell.textLabel?.text = firstnameValues[indexPath.row]
// Not working
//let memberDetails = members[indexPath.row]
//cell.detailTextLabel!.text = "Amount left: \(memberDetails.memberamount)"
}
return cell
}
func createFirstnameDict() {
for firstname in members {
var firstLetter = firstname.firstname
let firstnameKey = firstLetter.substring(to: firstLetter.characters.index(firstLetter.startIndex, offsetBy: 1))
if var memberValues = membersDict[firstnameKey] {
memberValues.append(firstLetter)
membersDict[firstnameKey] = memberValues
} else {
membersDict[firstnameKey] = [firstLetter]
}
}
memberSectionTitles = [String](membersDict.keys)
memberSectionTitles = memberSectionTitles.sorted { $0 < $1 }
}
func loadDataFromFirebase() {
let FBref = FIRDatabase.database().reference()
FBref.child("member-list").observeSingleEvent(of: .value, with: { (snapshot) in
var resultItem: [Member] = []
for item in snapshot.children {
let memberItem = Member(snapshot: item as! FIRDataSnapshot)
resultItem.append(memberItem)
}
self.members = resultItem
self.createFirstnameDict()
self.tableView.reloadData()
}) { (error) in
print(error.localizedDescription)
}
}
}
My Member model:
import Foundation
struct Member {
let firstname: String
let lastname: String
let email: String
let phonenumber: String
let socialsecuritynr: String
let memberamount: String
let addedByUser: String
let key: String
let ref: FIRDatabaseReference?
init(firstname: String, lastname: String, email: String, phonenumber: String, socialsecuritynr: String, memberamount: String, addedByUser: String, key: String = "") {
self.key = key
self.firstname = firstname
self.lastname = lastname
self.email = email
self.phonenumber = phonenumber
self.socialsecuritynr = socialsecuritynr
self.memberamount = memberamount
self.addedByUser = addedByUser
self.ref = nil
}
init(snapshot: FIRDataSnapshot) {
key = snapshot.key
let snapshotValue = snapshot.value as! [String: AnyObject]
firstname = snapshotValue["firstname"] as! String
lastname = snapshotValue["lastname"] as! String
email = snapshotValue["email"] as! String
phonenumber = snapshotValue["phonenumber"] as! String
socialsecuritynr = snapshotValue["socialsecuritynr"] as! String
memberamount = snapshotValue["memberamount"] as! String
addedByUser = snapshotValue["addedByUser"] as! String
ref = snapshot.ref
}
func toAnyObject() -> Any {
return ["firstname": firstname, "lastname": lastname, "email": email, "phonenumber": phonenumber, "socialsecuritynr": socialsecuritynr, "memberamount":memberamount, "addedByUser": addedByUser]
}
}
This is my TableView before and after:

Answer 1

The issue is arising from the placement of your methods that load the data which are wrongly in viewDidAppear:
loadDataFromFirebase()
createFirstnameDict()
This means that each time your view appears your data is loaded again and again. To fix the problem move these methods into viewDidLoad and you wont get the duplication issues. So you should now have:
override func viewDidLoad() {
super.viewDidLoad()
loadDataFromFirebase()
createFirstnameDict()
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
}

Answer 2

What I recommend you, is that you clear all your arrays that you populate on your before event listener. This way you make sure that when it come back from another view it will not have old data. Something like this:
self.members.removeAll()

Answer 3

You are displaying the data from membersDict in your cell.textlabel .
Each time your view(when you switch tabs) loads, it calls loadDataFromFirebase() .
Here, all the values get loaded again and get appended to your membersValues which you then store in membersDict.
A new instance of membersDict will not get created since you are not declaring them inside of viewDidLoad(). You have declared them inside the class but outside any function.
What append does is add an element at the end of the array. It does not overwrite the element. So if you have an array with two names, appending a name will make that your third name and not overwrite any existing names.
Each time you load the view, you are appending the names to an array that already consists of the names. This is what is causing the duplication.
Try printing the value of your membersDict or membersValues, to check if you are duplicating.
You can solve this by declaring an instance of membersDict locally such that an empty variable is created each time and use that to display data.
Hope this helps.

Answer 4

From my understanding and experience, you load firebase data in
override func viewDidLoad() {
super.viewDidLoad()
loadFirebaseData()
}
Your newly created data from any other view controller will appear on your table when you return to it, because your observers are still listening unless you have told them to stop listening when moving to other views.
Therefore, anytime new data appears in Firebase, your table will automatically display it.