Scroll to the latest inserted row in UITableView using Realm Objects - ios

Question

I have the following code which is working fine, it gets a list of items from a list in Realm called groceryList and displays them on a UITableView in descending order based on the productName. What I would like to be able to do is scroll to the latest inserted row/item in the table, right now when a new item is inserted the user may not see it since the items are alphabetically reordered and the latest item may not be visible on the tableView.
How can I scroll to the latest inserted row/item in a UITableView?
Realm Objects:
class Item:Object{
#objc dynamic var productName:String = ""
#objc dynamic var isItemActive = true
#objc dynamic var createdAt = NSDate()
}
class ItemList: Object {
#objc dynamic var listName = ""
#objc dynamic var createdAt = NSDate()
let items = List<Item>()
}
UITableView:
class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate{
var allItems : Results<Item>!
var groceryList : ItemList!
override func viewDidLoad() {
super.viewDidLoad()
groceryList = realm.objects(ItemList.self).filter("listName = %#", "groceryList").first
updateResultsList()
}
func updateResultsList(){
if let list = groceryList{
allItems = activeList.items.sorted(byKeyPath: "productName", ascending: false)
}
}
func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return allItems.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "reusableCell", for: indexPath) as! CustomCell
let data = allItems[indexPath.row]
cell.displayProductName.text = data.productName
return cell
}
}

Answer 1

You can use Realm notifications to know when the data source Results has been modified, then update your table view from there and do the scrolling as well.
class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {
var allItems: Results<Item>!
var groceryList: ItemList!
var notificationToken: NotificationToken? = nil
deinit {
notificationToken?.invalidate()
}
override func viewDidLoad() {
super.viewDidLoad()
groceryList = realm.objects(ItemList.self).filter("listName = %#", "groceryList").first
updateResultsList()
observeGroceryList
}
func updateResultsList(){
if let list = groceryList {
allItems = activeList.items.sorted(byKeyPath: "productName", ascending: false)
}
}
func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return allItems.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "reusableCell", for: indexPath) as! CustomCell
let data = allItems[indexPath.row]
cell.displayProductName.text = data.productName
return cell
}
func observeGroceryList() {
notificationToken = allItems.observe { [weak self] (changes: RealmCollectionChange) in
switch changes {
case .initial:
self?.tableView.reloadData()
case .update(_, let deletions, let insertions, let modifications):
// Query results have changed, so apply them to the UITableView
self?.tableView.beginUpdates()
self?.tableView.insertRows(at: insertions.map({ IndexPath(row: $0, section: 0) }),
with: .automatic)
self?.tableView.deleteRows(at: deletions.map({ IndexPath(row: $0, section: 0)}),
with: .automatic)
self?.tableView.reloadRows(at: modifications.map({ IndexPath(row: $0, section: 0) }),
with: .automatic)
self?.tableView.endUpdates()
if let lastInsertedRow = insertions.last {
self?.tableView.scrollToRow(at: insertions.last, at: .none, animated: true)
}
case .error(let error):
// An error occurred while opening the Realm file on the background worker thread
print("\(error)")
}
}
}
}

Answer 2

Add below code as extension of tableview.
extension UITableView {
func scrollToBottom() {
let sections = numberOfSections-1
if sections >= 0 {
let rows = numberOfRows(inSection: sections)-1
if rows >= 0 {
let indexPath = IndexPath(row: rows, section: sections)
DispatchQueue.main.async { [weak self] in
self?.scrollToRow(at: indexPath, at: .bottom, animated: true)
}
}
}
}
}
Now simply use it in your method:
func updateResultsList(){
if let list = groceryList{
allItems = activeList.items.sorted(byKeyPath: "productName", ascending: false
yourTableView.scrollToBottom()
}
}
Just use this method where you want, it should be scroll down.
yourTableView.scrollToBottom()