Ufdjrw

I have created a UITableView and adding the switch dynamically into each cell the basis is of requirement . if i select a switch and turn it on and immediately select next switch and turn it on, it's having an issue with the state of the switch its changing and a previously selected switch is getting off, its happening only if i select all the switch fast.

here is the image in this i am adding all the switches dynamically as per the data and if i on the first switch it data will load them in the other table . but if i select all the switch fast fast and turn them on some switch will stuck in to off state only . if i tap on the outside of the table its disappear and if again i load the table that time i can see all selected and previously enable (on) switch is turn off(not all but random its happen)

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell 
 var cell = tableView.dequeueReusableCell(withIdentifier: "cell")

 if let _ = cell else 
 cell = UITableViewCell(style: .default, reuseIdentifier: "cell")
 
 if let d = self.data 
 cell?.textLabel?.text = d[indexPath.row]
 let switchView = UISwitch(frame: .zero)
 switchView.setOn(self.isFolderIsAdded(folderName: d[indexPath.row]), animated: true)
 switchView.tag = indexPath.row // for detect which row switch Changed
 switchView.addTarget(self, action: #selector(self.switchChanged(_:)), for: .valueChanged)
 cell?.accessoryView = switchView

 
 return cell!


func isFolderIsAdded(folderName:String) -> Bool
 for val in listOfSelectedFolder
 if(folderName == val )
 return true
 
 
 return false;


@objc func switchChanged(_ sender : UISwitch!)
 if let d = self.data 
 if(sender.isOn)
 self.delegate?.selectedSubFolder(name: d[sender.tag])
 else 
 self.delegate?.deleteFilesFromFolder(folderName: d[sender.tag])
 
 

This is a reuse problem.
when you scroll the tableView, The cell is then reused.
the switch on it will be reset.

You need follow MVC Design patterns.
use a model to help you.
Like this

class CellModel 
 var name = ""
 var switchOn = false


var dataSource = [CellModel]()

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell 
 let cell = tableView.dequeueReusableCell(withIdentifier: "cell") as! CustomCell
 cell.model = dataSource[indexPath.row]
 return cell

class CustomCell: UITableViewCell 

 var model: CellModel? 
 didSet 
 switchView.isOn = model?.switchOn ?? false
 
 
 init(xxxx) 
 switchView.addTarget(self, action:#selector(self.switchChanged(_:)), for: .valueChanged)
 


 @objc func switchChanged(_ sender : UISwitch!)
 model.switchOn = sender.isOn
 
 

When Reusing a tableViewCell Always remember to use.

1- prepareForReuse method in tableViewCell class

2- write else conditions for all if conditions specially if you are updating any UI in if condition

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell 
var cell = tableView.dequeueReusableCell(withIdentifier: "cell")

if let _ = cell else 
 cell = UITableViewCell(style: .default, reuseIdentifier: "cell")

if let d = self.data 
 cell?.textLabel?.text = d[indexPath.row]
 let switchView = UISwitch(frame: .zero)
 switchView.setOn(self.isFolderIsAdded(folderName: d[indexPath.row]), animated: true)
 switchView.tag = indexPath.row // for detect which row switch Changed
 switchView.addTarget(self, action: #selector(self.switchChanged(_:)), for: .valueChanged)
 cell?.accessoryView = switchView

else
// Update your UI if data not found like turn your switch off etc ... 
 
 return cell!

3- Or It might be an issue of your simulator after update of Xcode 9.0 simulator are now not good as they were till Xcode 8.X

I am tried your code with some changes, it is working fine. It is not an issue with tableView.dequeueReusableCell. Please try the code below.

import UIKit

class FirstViewController: UIViewController,UITableViewDelegate, UITableViewDataSource



@IBOutlet weak var tableView: UITableView!
var listOfSelectedFolder = ["","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""]
var listOfSelectedFolder2 = ["sample text 0","sample text 1","sample text 2","sample text 4","sample text 5","sample text 6","sample text 7","sample text 8","sample text 9","sample text 10","sample text 11","sample text 12","sample text 13","sample text 14","sample text 15","sample text 16","sample text 17","sample text 18","sample text 19","sample text 20","sample text 21","sample text 22","sample text 23","sample text 24","sample text 25","sample text 26","sample text 27","sample text 28","sample text 29","sample text 30","sample text 31","sample text 32","sample text 33","sample text 34","sample text 35","sample text 36","sample text 37","sample text 38","sample text 39","sample text 40"]

override func viewDidLoad() 
 super.viewDidLoad()
 self.tableView.delegate = self
 self.tableView.dataSource = self
 // Do any additional setup after loading the view, typically from a nib.



override func didReceiveMemoryWarning() 
 super.didReceiveMemoryWarning()
 // Dispose of any resources that can be recreated.


/// tableview datasouce methodes

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int 
 return listOfSelectedFolder2.count

func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat 
 return 50


func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell 
 var cell = tableView.dequeueReusableCell(withIdentifier: "cell")

 if let _ = cell else 
 cell = UITableViewCell(style: .default, reuseIdentifier: "cell")
 
 let foldername = listOfSelectedFolder2[indexPath.row]
 cell?.textLabel?.text = foldername
 let switchView = UISwitch(frame: .zero)
 switchView.setOn(self.isFolderIsAdded(folderName: foldername), animated: true)
 switchView.tag = indexPath.row // for detect which row switch Changed
 switchView.addTarget(self, action: #selector(self.switchChanged(_:)), for: .valueChanged)
 cell?.accessoryView = switchView

 return cell!

func isFolderIsAdded(folderName:String) -> Bool

 return listOfSelectedFolder.contains(folderName);


@objc func switchChanged(_ sender : UISwitch!)
 if(sender.isOn)

 self.listOfSelectedFolder.insert(self.listOfSelectedFolder2[sender.tag], at: sender.tag)
 else 
 self.listOfSelectedFolder.remove(at: sender.tag)
 self.listOfSelectedFolder.insert("", at: sender.tag)
 

In case you still have the same issue, maybe the UI updates happening on the background thread. So make sure the UI updating code is running on the main thread.

dispatch_async(dispatch_get_main_queue(), code)

or

DispatchQueue.main.async code