Reload TableView only at new rows once user scrolls to bottom - swift

Question

I am trying to append new data to Tableview and only reload the Tableview for the new data added.
My app has been crashing giving me this error: "attempt to delete row 19 from section 0 which only contains 10 rows before the update'"
I would like to reload those rows once the asynchronous function contentQueryContinuous() is completed.
Here is my code:
//Once User Scrolls all the way to bottom, beginContentBatchFetch() is called
func scrollViewDidScroll(_ scrollView: UIScrollView) {
let offsetY = scrollView.contentSize.height
let contentHeight = scrollView.contentSize.height
if offsetY > contentHeight - scrollView.frame.height {
beginContentBatchFetch()
}
}
//Content Batch Fetch looks up to 10 new elements, tries to append to current array's, and then reload's tableview only for those new elements
func beginContentBatchFetch() {
contentFetchMore = true
ProgressHUD.show()
let oldcount = contentObjectIdArray.count
var IndexPathsToReload = [IndexPath]()
var startIndex = Int()
var endIndex = Int()
DispatchQueue.main.asyncAfter(deadline: .now() + 1.0) {
//Calls self.contentQueryContinous which adds new elements
self.contentQueryContinous()
let newElements = self.contentObjectIdArray.count - oldcount
startIndex = oldcount
endIndex = self.contentObjectIdArray.count
for index in startIndex..<endIndex {
let indexPath = IndexPath(row: index, section: 0)
IndexPathsToReload.append(indexPath)
}
if newElements > 0 {
self.MyTableView.reloadRows(at: IndexPathsToReload, with: .fade)
}
ProgressHUD.dismiss()
}
}
Here is contentQueryContinous()
func contentQueryContinous() {
if contentObjectIdArray.count != 0 {
contentSkip = contentObjectIdArray.count
let query = PFQuery(className: "ContentPost")
query.whereKey("Spot", equalTo: SpotText)
query.limit = 10
query.skip = contentSkip
query.addDescendingOrder("createdAt")
query.findObjectsInBackground(block: { (objects: [PFObject]?,error: Error?) in
if let objects = objects {
for object in objects {
let ProfileImageFile = object["ProfileImage"] as? PFFileObject
let urlString = ProfileImageFile?.url as! String
if let url = URL(string: urlString) {
let data = try? Data(contentsOf: url)
if let imageData = data {
self.contentPostProPicUrlArray.append(urlString as NSString)
self.contentPostProPicImageCache.setObject(UIImage(data: imageData)!, forKey: urlString as NSString)
}
}
if object["Post"] != nil && object["UserLikes"] != nil && object["Username"] != nil && object["UserTime"] != nil {
self.contentPostArray.append(object["Post"] as! String)
self.contentLikeArray.append(object["UserLikes"] as! Int)
self.contentUsernameArray.append(object["Username"] as! String)
self.contentTimeArray.append(object["UserTime"] as! String)
self.contentObjectIdArray.append(object.objectId!)
}
}
print(self.contentPostArray)
}
})
}
}

Answer 1

You are trying to reload a cell that is not on the table. Try inserting it. Also, you are risking a race condition.
From the docs
Reloading a row causes the table view to ask its data source for a new cell for that row. The table animates that new cell in as it animates the old row out. Call this method if you want to alert the user that the value of a cell is changing.