Update Realtime data to UITableview row in swift - ios

Question

I have the websocket server that server push the data every two seconds based on my subscription. I need to update the row based on the in the tableview.currently I am using Starscream module for websocket implementation. how to update specific rows value to every two seconds
import UIKit
import Starscream
struct Stocks: Codable {
let changepercent: String
let changeprice: String
let close: String
let currentprice: String
let high: String
let id: Int
let low: String
let name: String
let `open`: String
let type: String
let instid: String
let exchange: String
}
class ViewController: UIViewController, WebSocketDelegate,UITableViewDelegate,UITableViewDataSource {
#IBOutlet weak var stocktableView: UITableView!
var arrContacts = [Stocks]()
var socket: WebSocket!
override func viewDidLoad() {
super.viewDidLoad()
var request = URLRequest(url: URL(string: "ws://192.168.18.97:8080/sss/landingstream")!)
//var request = URLRequest(url: URL(string: "ws://192.168.18.97:8080/Setrega/landingstream")!)
request.timeoutInterval = 5
socket = WebSocket(request: request)
socket.delegate = self
socket.connect()
}
// MARK: Websocket Delegate Methods.
func websocketDidConnect(socket: WebSocketClient) {
print("websocket is connected")
}
func websocketDidDisconnect(socket: WebSocketClient, error: Error?) {
if let e = error as? WSError {
print("websocket is disconnected: \(e.message)")
} else if let e = error {
print("websocket is disconnected: \(e.localizedDescription)")
} else {
print("websocket disconnected")
}
}
func websocketDidReceiveMessage(socket: WebSocketClient, text: String) {
print("Received text: \(text)")
let decoder = JSONDecoder()
do {
let iexEvent: Stocks = try decoder.decode(Stocks.self, from: text.data(using: .utf8)!)
DispatchQueue.main.async {
self.stocktableView.reloadData()
}
} catch {
print(error)
}
}
func websocketDidReceiveData(socket: WebSocketClient, data: Data) {
print("Received data: \(data.count)")
}
// MARK: Write Text Action
#IBAction func writeText(_ sender: UIBarButtonItem) {
socket.write(string: "{\"requestType\": \"INSTRUMENT_PRICE\",\"topic\": \"SBIN\"}")
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return self.arrContacts.count;
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "StocksCell", for: indexPath)
cell.textLabel?.text = arrContacts[indexPath.row].changeprice
return cell
}
// MARK: Disconnect Action
#IBAction func disconnect(_ sender: UIBarButtonItem) {
if socket.isConnected {
sender.title = "Connect"
socket.disconnect()
} else {
sender.title = "Disconnect"
socket.connect()
}
}
}

Answer 1

Instead of this:
DispatchQueue.main.async {
self.stocktableView.reloadData()
}
Try to find the rows that were changed with this function:
final func indexesOfStocks(stocks:[Stocks]) -> [Int] {
return stocks.reduce([]) { (currentResult, currentStocks) in
if let currentStockIndex = self.arrContacts.index(where: { currentStocks.id == $0.id }) {
return currentResult + [currentStockIndex]
}
return currentResult
}
}
Update property arrContacts:
final func updateArrContacts(indexesOfStocksValue:[Int], iexEvents:[Stocks]) {
for i in stride(from: 0, to: indexesOfStocksValue.count, by: 1) {
self.arrContacts[indexesOfStocksValue[i]] = iexEvents[i]
}
}
And reload rows for updates items only:
final func updateRows(stocksIndexes:[Int]) {
DispatchQueue.main.async {
self.stocktableView.performBatchUpdates({
let indexesToUpdate = stocksIndexes.reduce([], { (currentResult, currentStocksIndex) -> [IndexPath] in
if currentStocksIndex < self.stocktableView.numberOfRows(inSection: 0) {
return currentResult + [IndexPath.init(row: currentStocksIndex, section: 0)]
}
return currentResult
})
self.stocktableView.reloadRows(at: indexesToUpdate, with: UITableViewRowAnimation.automatic)
}) { (_) in
}
}
}
Now you can update rows with that code:
let indexesOfStocksValue = self.indexesOfStocks(stocks: iexEvents) // iexEvents is an array of Stocks
self.updateArrContacts(indexesOfStocksValue: indexesOfStocksValue, iexEvents: iexEvents)
self.updateRows(stocksIndexes: indexesOfStocksValue)
This solution is based on idea that after websocketDidReceiveMessage: only existing items in arrContacts should be updated. No new items will be added and no items will be removed.