Swift UIRefresh Control Drag to refresh in UITableView causes app crash - ios

Question

I have a UIRefreshControll, inside my TableView. All works fine, but if i pull the tableview too fast, the app crashes.
Error: Fatal error: Index out of range
When i call the function refreshData from a Button, the crash doesnt appear. Is kind of weird because refreshControll doesnt do something different than calling a action.
I hope somebody can help me.
private let refreshControl = UIRefreshControl()
refreshControl.addTarget(self, action: #selector(self.refreshData), for: .valueChanged)
if #available(iOS 10.0, *) {
self.tableView.refreshControl = self.refreshControl
} else {
self.tableView.addSubview(self.refreshControl)
}
#objc private func refreshData() {
if isRefreshing {
self.refreshControl.endRefreshing()
return
}
isRefreshing = true
print("refresh")
guard let url = URL(string: taskURL) else {
return
}
let request = URLRequest(url: url)
urlSessionBackground.dataTask(with: request) { (dataOpt, response, error) in
if error != nil {
DispatchQueue.main.async {
let alert = UIAlertController(title: "Loading Error", message: "No Internet Connection. Please try again later.", preferredStyle: .alert)
alert.addAction(UIAlertAction(title: "Ok", style: .default, handler: {(action: UIAlertAction!) in
self.refreshControl.endRefreshing()
}))
self.present(alert, animated: true)
}
return
}else {
self.data.removeAll()
self.userImage.removeAll()
self.currentData.removeAll()
self.taskDetails.removeAll()
}
guard let dataNew = dataOpt else {
return
}
let appdata = try? JSONDecoder().decode(TaskList.self, from: dataNew)
for data in appdata!{
self.data.append(CellData.init(image: UIImage(named: "Profile"), message: data.name, checkImage: data.status))
self.userImage.append("")
self.taskDetails.append(TaskDetails.init(status: data.status, assigned: data.assigneUid, time: data.duedateTsUTC, priority: data.priority, desc: data.desc, uid: data.uid))
}
self.currentData = self.data
DispatchQueue.main.async {
self.tableView.reloadData()
self.searchBar.text = ""
self.isRefreshing = false
self.refreshControl.endRefreshing()
}
}.resume()
}
Fixed it: Used temporary variables to save data and use afterwards. Deleting the data was the problem.

Answer 1

Try this
if error != nil {
DispatchQueue.main.async {
let alert = UIAlertController(title: "Loading Error", message: "No Internet Connection. Please try again later.", preferredStyle: .alert)
alert.addAction(UIAlertAction(title: "Ok", style: .default, handler: {(action: UIAlertAction!) in
self.refreshControl.endRefreshing()
}))
self.present(alert, animated: true)
}
return
}else {
if self.data != nil{
self.data.removeAll()
}
if self.userImage != nil{
self.userImage.removeAll()
}
if self.currentData != nil{
self.currentData.removeAll()
}
if self.taskDetails != nil{
self.taskDetails.removeAll()
}
}

Answer 2

Just try this
var dataTask: URLSessionDataTask?
let defaultSession = URLSession(configuration: .background)
#objc private func refreshData() {
if isRefreshing {
self.refreshControl.endRefreshing()
return
}
isRefreshing = true
print("refresh")
guard let url = URL(string: taskURL) else {
return
}
dataTask?.cancel()
let request = URLRequest(url: url)
dataTask =
defaultSession.dataTask(with: url) { [weak self](dataOpt, response, error) in
defer {
self?.dataTask = nil
}
if let error = error {
DispatchQueue.main.async {
let alert = UIAlertController(title: "Loading Error", message: "No Internet Connection. Please try again later.", preferredStyle: .alert)
alert.addAction(UIAlertAction(title: "Ok", style: .default, handler: {(action: UIAlertAction!) in
self.refreshControl.endRefreshing()
}))
self.present(alert, animated: true)
}
return
} else if
let data = dataOpt,
let response = response as? HTTPURLResponse,
response.statusCode == 200 {
self.data.removeAll()
self.userImage.removeAll()
self.currentData.removeAll()
self.taskDetails.removeAll()
let appdata = try? JSONDecoder().decode(TaskList.self, from: data)
for data in appdata!{
self.data.append(CellData.init(image: UIImage(named: "Profile"), message: data.name, checkImage: data.status))
self.userImage.append("")
self.taskDetails.append(TaskDetails.init(status: data.status, assigned: data.assigneUid, time: data.duedateTsUTC, priority: data.priority, desc: data.desc, uid: data.uid))
}
self.currentData = self.data
DispatchQueue.main.async {
self.tableView.reloadData()
self.searchBar.text = ""
self.isRefreshing = false
self.refreshControl.endRefreshing()
}
}
}
dataTask?.resume()
}