Tableview keeps going back to top? After leaving to "detailed" vc? - swift

Question

How can I prevent the view controller from starting from the top of the feed when a user leaves and goes back?
Basically, I have the main VC and a detailed VC. When the user selects a cell, it should jump to the detailed VC. If she/he goes back, it should leave her back to where she/he was.
I get that my code is calling "reload Data" every time the VC loads, but what other options do I have then if I don't call that method?
Here's an image of my main storyboard if it helps. Main VC(left) is the feed tableView where the user can tap on the cell. When he/she taps on the cell, it "segues" to the comment table VC (right). When he/she is done commenting she/he can go back to the main VC and continuing going down the feed. (ideally, except it keeps loading from the newest post, rather than segueing the user back to where she/he was down in the feed)
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "postCell", for: indexPath) as! PostCell
let post: PostModel
post = postList[indexPath.row]
func set(post: PostModel) {
ImageService.downloadImage(withURL: post.author.patthToImage) { image in
cell.profileImage.image = image
}
}
set(post: postList[indexPath.row])
cell.descriptionLabel.numberOfLines = 0 // line wrap
cell.descriptionLabel.lineBreakMode = NSLineBreakMode.byWordWrapping
cell.descriptionLabel.text = post.message
cell.authorLabel.text = post.author.username
cell.timeLabel.text = post.createdAt.calendarTimeSinceNow()
//takes care of post image hidding and showing
if self.postList[indexPath.row].pathToImage != "" {
cell.postImage.isHidden = false
cell.postImage?.downloadImage(from: self.postList[indexPath.row].pathToImage)
} else {
cell.postImage.isHidden = true
}
if cell.postImage.isHidden == true {
cell.postImage.frame = CGRect(x: 0, y: 0, width: 0, height: 0)
}
return cell
}
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
let post: PostModel
post = postList[indexPath.row]
myIndex = indexPath.row
myPost = post.postID!
performSegue(withIdentifier: "segue", sender: self)
print(myIndex)
print(post.postID)
}
override func viewDidLoad() {
super.viewDidLoad()
beginBatchFetch()
}
func beginBatchFetch() {
fetchingMore = true
fetchPosts { newPosts in
self.postList.append(contentsOf: newPosts)
self.endReached = newPosts.count == 0
self.fetchingMore = false
self.tableViewPost.reloadData()
}
}
func fetchPosts(completion: #escaping(_ postList:[PostModel])->()) {
ref = Database.database().reference().child("posts")
var queryRef:DatabaseQuery
let lastPost = self.postList.last
if lastPost != nil {
let lastTimestamp = lastPost!.createdAt.timeIntervalSince1970 * 1000
queryRef = ref.queryOrdered(byChild: "timestamp").queryEnding(atValue: lastTimestamp).queryLimited(toLast:20)
} else {
queryRef = ref.queryOrdered(byChild: "timestamp").queryLimited(toLast:20)
}
queryRef.observeSingleEvent(of: .value, with: { snapshot in
var tempPosts = [PostModel]()
for child in snapshot.children {
if let childSnapshot = child as? DataSnapshot,
let dict = childSnapshot.value as? [String:Any],
let author = dict["author"] as? [String:Any],
let uid = author["uid"] as? String,
let username = author["username"] as? String,
let fullname = author["fullname"] as? String,
let patthToImage = author["patthToImage"] as? String,
let url = URL(string:patthToImage),
let pathToImage = dict["pathToImage"] as? String,
let likes = dict["likes"] as? Int,
let postID = dict["postID"] as? String,
let message = dict["message"] as? String,
let genre = dict["genre"] as? String,
let timestamp = dict["timestamp"] as? Double {
let userProfile = UserProfile(uid: uid, fullname: fullname, username: username, patthToImage: url)
let post = PostModel(genre: genre, likes: likes, message: message, pathToImage: pathToImage, postID: postID, userID: pathToImage, timestamp: timestamp, id: childSnapshot.key, author: userProfile)
tempPosts.insert(post, at: 0)
}
}
//first two
self.postList = tempPosts
self.tableViewPost.reloadData()
// return completion(tempPosts)
})

Answer 1

The issue, as Matt pointed out, is that you are segueing to the detailVC and then segueing back to the original VC. This is creating a new instance of the original VC.
What you should do, in your VC with the table view, is instantiate and present the destination view controller when a cell is selected. So you should replace performSegue(withIdentifier: "segue", sender: self) with something like:
let storyboard = UIStoryboard(name: "Main", bundle: .main)
var destinationVC = (storyboard.instantiateViewController(withIdentifier: "DestinationVC") as! DestinationViewController)
present(destinationVC!, animated: ture, completion: nil)
NOTE: View Controller storyboard identifiers can be set in the interface builder. So, if you are wanting to use this line: var destinationVC = (storyboard.instantiateViewController(withIdentifier: "DestinationVC") as! DestinationViewController), you will first have to set the Storyboard ID in the interface builder:
Now, within your destination view controller, instead of segueing when your done button is pressed, you want to use the dismiss method to dismiss the presented view controller.
class DestinationViewController: UIViewController {
#IBAction func backButtonPressed(_ sender: Any) {
dismiss(animated: true, completion: nil)
}
}
Now, the original VC with the table view stays in memory while the destination VC is presented over it. When the user presses the "back" button, it will dismiss the destination VC and the original VC should reappear as you left it.

Answer 2

"I added a "back" button to segue back" That's the problem. The way to go back is to call dismiss — not use a second segue (unless it is a special "unwind" segue, but you don't know how to do that).