TableView moves down when fetching data - ios

Question

When I scroll almost to the end of the current table view, it loads more data, and the problem is after reloadData() it almost instantly moves to another cell. For example, if I stopped scrolling on the 12th cell, tableView moves to the 15th. The same with 22 and 25 etc. I don't want my tableView to jump over cells. How can I repair it?
How I check whether its time to load more data:
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "previewCell") as! postsCell
let photosForFirstPost = photoURLs[indexPath.row + 1]
//print(photoURLs[0])
if photosForFirstPost?.count != 0 && photosForFirstPost != nil {
let url = photosForFirstPost![0]
// cell.imagePreview.kf.setImage(with: url)
let resource = ImageResource(downloadURL: photosForFirstPost![0], cacheKey: String(describing: photosForFirstPost![0]))
// print(ImageCache.default.isImageCached(forKey: String(describing: photosForFirstPost![0])))
cell.imagePreview.kf.setImage(with: resource)
} else {
cell.imagePreview.image = UIImage(named: "harry")
}
cell.separatorLine.backgroundColor = .blue
cell.themeName.text = "Theme name"
cell.readTime.text = "3 mins read"
cell.textPreview.text = realPosts[indexPath.row].text
if postsTableView.indexPathsForVisibleRows?.first?.row == realPosts.count - 3 {
var arrayOfIndexes = [IndexPath]()
for i in 0...9 {
arrayOfIndexes.append(IndexPath(row: realPosts.count + i, section: 0))
}
requestTenPosts(indexPath: arrayOfIndexes)
}
return cell
}
How I request data at the launch:
func requestForPosts() {
guard let requestURL = URL(string: "https://api.vk.com/method/wall.get?owner_id=\(groupId)&count=\(howMuchPosts)&access_token=\(serviceKey)&v=\(versionOfMethod)&offset=\(offset)") else { return }
do {
self.posts = [try Welcome(fromURL: requestURL)]
realPosts = self.posts[0].response.items
searchPhotos(arrayOfItems: self.realPosts)
offset += howMuchPosts
} catch {
print(error)
}
}
How I request for more data:
func requestTenPosts(indexPath: [IndexPath]) {
guard let requestURL = URL(string: "https://api.vk.com/method/wall.get?owner_id=\(groupId)&count=\(10)&access_token=\(serviceKey)&v=\(versionOfMethod)&offset=\(offset)") else { return }
DispatchQueue.global().async {
do {
self.offset += 10
for howMuchKeysToADD in (self.offset...self.offset + 10) {
self.textOfAPost.updateValue("", forKey: howMuchKeysToADD)
self.photoURLs.updateValue([], forKey: howMuchKeysToADD)
}
var forAMoment = try Welcome(fromURL: requestURL)
var arrayForAMoment: [Item] = []
for i in 0...9 {
self.realPosts.append(forAMoment.response.items[i])
arrayForAMoment.append(forAMoment.response.items[i])
}
print(arrayForAMoment)
print("searchPhotos is called")
self.searchPhotos(arrayOfItems: arrayForAMoment)
DispatchQueue.main.async {
self.postsTableView.reloadData()
}
} catch {
print(error)
}

Answer 1

if postsTableView.indexPathsForVisibleRows?.first?.row == realPosts.count - 3 {
var arrayOfIndexes = [IndexPath]()
for i in 0...9 {
arrayOfIndexes.append(IndexPath(row: realPosts.count + i, section: 0))
}
requestTenPosts(indexPath: arrayOfIndexes)
}else{return}
or use simple else{} and don't forgot to give cell.tag = [indexpath.row]

Answer 2

Instead of reloading the data, can you try inserting the rows at the bottom. Since you already have access to all the index paths, it should not be difficult and table view should not move.
DispatchQueue.main.async {
//self.postsTableView.reloadData()
self.postsTableView.beginUpdates()
self.postsTableView.insertRows(at: indexPath, with: .left)
self.postsTableView.endUpdates()
}