[__NSArray0 objectAtIndex:]: index 0 beyond bounds for empty NSArray - ios

Question

I am getting JSON data from an API and display it in a tableView. When user scrolls at the last row, the next page will be added to the current data.
But I am getting this error when next page data is added.
[__NSArray0 objectAtIndex:]: index 0 beyond bounds for empty NSArray
func loadUser(_ currentPage:Int=1){
APIService.loadUser(currentPage, size: 100, callback: { data in
if let data = data["user"].arrayValue as [JSON]?{
self.jsonData?.append(contentsOf: data
self.tableView.reloadData()
self.hideLoadingInView(view: self.view)
}
})
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return self.jsonData?.count ?? 0
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "UserCell") as! UserTableViewCell
cell.user = self.jsonData?[indexPath.row]
if !isLoading && (indexPath.row == self.jsonData!.count - 1){
currentPage += 1
loadUser(currentPage)
}
return cell
}

Answer 1

I would suggest few potential fixes:
Add Exception Breakpoint to your project, so you can better debug your particular issue. It's very useful tip: https://www.natashatherobot.com/xcode-debugging-trick/ You'll probably find out what's wrong with this.
Move the UI manipulation inside the API call response into the DispatchQueue.main.async { ... } block, to be sure the UI is manipulated on the main thread. Otherwise it can cause weird behavior and maybe also your issue.
Move the check if you need to fetch another page from API to the tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) function. Some people do recommend to do it in scrollViewDidScroll delegated method of UIScrollView.
Then it will look like this.
func loadUser(_ currentPage:Int=1){
APIService.loadUser(currentPage, size: 100, callback: { data in
if let data = data["user"].arrayValue as [JSON]?{
DispatchQueue.main.async {
self.jsonData?.append(contentsOf: data)
self.tableView.reloadData()
self.hideLoadingInView(view: self.view)
}
}
})
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return self.jsonData?.count ?? 0
}
func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
if !isLoading && (indexPath.row == self.jsonData!.count - 1){
currentPage += 1
loadUser(currentPage)
}
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "UserCell") as! UserTableViewCell
cell.user = self.jsonData?[indexPath.row]
return cell
}