'Array Index out of Range' on 'RefreshControl' - ios

Question

I have a TableView where I am fetching data from api. Everything working fine with fetching/displaying data and pagination/infinite-scroll. However, when I try to use my RefreshControl, it crashes with an error:
Array index out of range
var theRefreshControl: UIRefreshControl!
var results: [JSON]! = []
// more stuff..
func refresh(sender: AnyObject) {
if isFirstLoad == false {
self.results = []
currentPage = 1
getPosts()
}
self.theRefreshControl.endRefreshing()
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell : PostCell = tableView.dequeueReusableCellWithIdentifier("PostCell") as! PostCell
cell.delegate = self
print(indexPath.row) // check below.
let post = self.results![indexPath.row] // 'array index out of range' here.
}
To get more detail about the error, I tried adding print(indexPath.row). What I receive is, I receive from 0 to 10 in first load, and then as soon as I refresh, it gets weird:
Also, when I click on the (i):
{length = 2, path = 0 - 9}
Interestingly, exactly same approach works in my other TableViewControllers, only this one is bugging. What may be the problem?
func getPosts() {
isLoading = true
Alamofire.request(.GET, link & params: ["page":"\(currentPage ?? 1)"])
.responseJSON { response in
// error checks
if let data = json["data"].arrayValue as [JSON]? {
self.lastPage = json["last_page"].int!
self.currentPage = json["current_page"].int!
if self.currentPage == 1 {
self.results = data
self.tableView.reloadData()
} else {
var currentCount = self.results!.count;
var indxesPath : [NSIndexPath] = [NSIndexPath]()
for result in data {
indxesPath.append(NSIndexPath(forRow:currentCount,inSection:0));
self.results?.append(result)
currentCount++
}
self.tableView.insertRowsAtIndexPaths(indxesPath, withRowAnimation: UITableViewRowAnimation.Bottom)
}
Edit: Please note that I tried results.removeAll() as well as results.removeAll(keepCapacity: false) in refresh button action function, but no luck. I am still getting the same error and same log for `print(indexPath.row) - 0 to 10 in first load, and in refresh, weirdly 6, 7, 8, [], 9

Answer 1

Swift 3.0 - Same issue here, solved in a similar way to #mcclux but with one less step.
Use the inbuilt UIRefreshControl.
var refreshControl: UIRefreshControl!, then within viewDidLoad configure it:
refreshControl = UIRefreshControl.init()
refreshControl.attributedTitle = NSAttributedString(string: "Pull to refresh")
refreshControl.addTarget(self, action: #selector(yourViewControllerName.yourFunctionToCallOnRefresh), for: UIControlEvents.valueChanged)
tableView.addSubview(refreshControl)
Then you can wrap your code within cellForRowAt indexPath with
if !self.refreshControl.isRefreshing {
...
}
Worked perfectly for me after struggling through it crashing for hours. Hope this helps!

Answer 2

I had a similar issue; it was caused in my case by tableView being called during the refresh, during the period when the content was being reset. Because the index was empty for a period, the app was occasionally throwing index out of range. It didn't happen every time. I solved it by creating a boolean var (isRefreshing) that gets set to true when the refresh starts and then set to false once the refresh is over. Inside of tableView() I have a wrapper for the functionality. In your case it would look like:
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
if !self.isRefreshing {
let cell : PostCell = tableView.dequeueReusableCellWithIdentifier("PostCell") as! PostCell
cell.delegate = self
print(indexPath.row) // check below.
let post = self.results![indexPath.row] // 'array index out of range' here.
}
}
Edit: here's how I'm using it. The cell creation and return are outside of the if:
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("SessionTableViewCell", forIndexPath: indexPath) as! SessionTableViewCell
if !self.isReloading {
...
}
return cell
}

Answer 3

Solved my problem by deletingself.results = [] from refresh() function. Interestingly, if I empty the array before I refresh, it was creating a problem, but if I directly overwrite the data in the array, it works!

Answer 4

I was facing similar issue when the backing array was emptied like what you did w/ self.results = []. In my finding, there are 2 additional ways to solve this issue.
//1. is to reload table view as soon as you empty the array
func refresh(sender: AnyObject) {
if isFirstLoad == false {
self.results = []
self.tableView.reloadData()
currentPage = 1
getPosts()
}
self.theRefreshControl.endRefreshing()
}
//2. is to delay the execution of the code inside the if scope to give enough time for the table view to get up to date on the count of the results array
func refresh(sender: AnyObject) {
if isFirstLoad == false {
self.delayExecutionByMilliseconds(500) {
self.results = []
currentPage = 1
getPosts()
}
}
self.theRefreshControl.endRefreshing()
}
func delayExecutionByMilliseconds(_ delay: Int, for anonFunc: #escaping () -> Void) {
let when = DispatchTime.now() + .milliseconds(delay)
DispatchQueue.main.asyncAfter(deadline: when, execute: anonFunc)
}

Answer 5

In your refresh function, add self.tableView.reloadData() after cleaning your arrays, and before the function getPosts()