call deleteRowsAtIndexPaths multiple times - ios

Question

There are several questions about this problem. I have tried all of the suggested answers but nothing has worked yet.
So I have this func which decline offers that a user receives. I can decline the offers and delete the cell rows but when there is only one cell left I get fatal error: Index out of range
func declineButtonTapped(sender: AnyObject) {
self.view.userInteractionEnabled = false
let buttonRow = sender.tag // this is the tag from my custom cell button
let offer = offers[buttonRow] // I get the error here
let loadingNotification = MBProgressHUD.showHUDAddedTo(self.view, animated: true)
loadingNotification.mode = MBProgressHUDMode.Indeterminate
loadingNotification.labelText = "declining offer...."
let myUrl = NSURL(string: "\(ipAddress)/api/v1.0/offers.php")
let request = NSMutableURLRequest(URL: myUrl!)
request.HTTPMethod = "POST"
let postString = "id=\(offer.id!)&action=decline&offer_id=\(offer.offer_id!)"
request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: true)
let task = NSURLSession.sharedSession().dataTaskWithRequest(request)
{ data, response, error in
if error != nil {
let messageToDisplay = error
self.view.userInteractionEnabled = true
return
}
do{
let json = try NSJSONSerialization.JSONObjectWithData(data!, options: .MutableContainers) as? NSDictionary
if let parseJSON = json{
let resultValue = parseJSON["status"] as? String
if resultValue == "Success"{
dispatch_async(dispatch_get_main_queue()) {
print("before count is \(self.offers.count)") // before the error the count is 2 here
self.offers.removeAtIndex(buttonRow) //update my model
self.tableView.deleteRowsAtIndexPaths([NSIndexPath(forRow: buttonRow, inSection: 0)], withRowAnimation: UITableViewRowAnimation.Fade)
print("after count is \(self.offers.count)") //then the count is 1 here
MBProgressHUD.hideAllHUDsForView(self.view, animated: true)
self.view.userInteractionEnabled = true
}
}else{
//no success
}
}
} catch{
}
}
task.resume()
}
inside cellForRowAtIndexPath I assign the tag value of the button
offerCell.declineButton.tag = indexPath.row
offerCell.declineButton.addTarget(self, action: #selector(OpenDealsDetailsViewController.declineButtonTapped(_:)), forControlEvents: UIControlEvents.TouchUpInside)
******UPDATE*****
I think I found the error. When I print
print("button row is\(buttonRow)") the number don't get updated. So the first time it calls the correct row but the second times it keep the indexPath.row it had when declineButtonTapped was called the first time
button row is0
before count is 2
after count is 1
button row is1 // this of course should be 0 as there is only one cell left
fatal error: Index out of range
if I try to do
self.offers.removeAtIndex(buttonRow)
self.tableView.deleteRowsAtIndexPaths([NSIndexPath(forRow: buttonRow, inSection: 0)], withRowAnimation: UITableViewRowAnimation.Fade)
self.tableView.reloadData()
I get the following error:
Invalid update: invalid number of rows in section 0. The number of rows contained in an existing section after the update (1) must be equal to the number of rows contained in that section before the update (1), plus or minus the number of rows inserted or deleted from that section (0 inserted, 1 deleted) and plus or minus the number of rows moved into or out of that section (0 moved in, 0 moved out).

Answer 1

You either shouldn't use tags or you should reload the table view fully after each change. Alternately you could iterate the visible cells and update their tag values.
If you were to always and only delete the last row from the table it'd be fine. As soon as you delete an earlier row all the rows after that now have an incorrect tag value. So, when you go to the last row it doesn't actually exist at that tag, and any other invalid rows will result in you deleting the wrong item from the server.
A better approach is to pass the cell an instance of a class which can action the deletion and call back to the view controller with details of the update made. The view controller can then update its data source and the table view. In this way you separate the table index path from the action you're going to take on the data.