adding Button in last tableView Cell shown twice when scrolling - swift

Question

Using Swift4, iOS11.2.1, Xcode9.2,
I successfully added a custom button to the last cell of a tableView. (the button is used to add cells in the tableView - this also works fine...) - see Screenshot-1.
But now the issue: When adding more cells (i.e. more than fit in the tableView-height), and if you scroll to the top, then there is a second cell that shows this button - see Screenshot-2.
(see code below....)
Here are the two screenshots:
How can I get rid of the extra button ????
(it seems that a cell is reused and the button is partly drawn. The cut-off can be explained since the height of the last cell is made bigger than the other cells. But still, there shouldn't be parts of buttons in any other cell than the very last one...even when scrolling up).
Any help appreciated !
Here is my code (or excerts of it...):
override func viewDidLoad() {
super.viewDidLoad()
// define delegates
self.fromToTableView.dataSource = self
self.fromToTableView.delegate = self
// define cell look and feel
self.addButton.setImage(UIImage(named: "addButton"), for: .normal)
self.addButton.addTarget(self, action: #selector(plusButtonAction), for: .touchUpInside)
//...
self.fromToTableView.reloadData()
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
guard let resItems = resItems else {
self.rowCount = 0
return 0
}
self.rowCount = resItems.count - 1
return resItems.count
}
func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
if(indexPath.row == (self.rowCount)) {
return 160
} else {
return 120
}
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = fromToTableView.dequeueReusableCell(withIdentifier: "SettingsCell") as? SettingsCustomTableViewCell
// configure the cell
cell?.configureCell(tag: indexPath.row)
// fill cell-data
if let resItem = self.resItems?[indexPath.row] {
cell?.connectionItem = resItem
}
// add addButton to last cell
if(indexPath.row == (self.rowCount)) {
// add addButton
cell?.contentView.addSubview(self.addButton)
// scroll to last cell (that was just added)
// First figure out how many sections there are
let lastSectionIndex = self.fromToTableView.numberOfSections - 1
// Then grab the number of rows in the last section
let lastRowIndex = self.fromToTableView.numberOfRows(inSection: lastSectionIndex) - 1
// Now just construct the index path
let pathToLastRow = IndexPath(row: lastRowIndex, section: lastSectionIndex)
// Scroll to last cell
self.fromToTableView.scrollToRow(at: pathToLastRow as IndexPath, at: UITableViewScrollPosition.none, animated: true)
}
return cell!
}

Answer 1

You already figured out what the problem is :)
As you say here:
it seems that a cell is reused and the button is partly drawn
And that is exactly what happens here. You have a pool of UITableViewCell elements, or in your case SettingsCustomTableViewCell. So whenever you say:
let cell = fromToTableView.dequeueReusableCell(withIdentifier: "SettingsCell") as? SettingsCustomTableViewCell
Then, as the name implies, you dequeue a reusable cell from your UITableView.
That also means that whatever you may have set on the cell previously (like your button for instance) stays there whenever you reuse that specific instance of a cell.
You can fix this in (at least) three ways.
The Hack
In your tableView(_:cellForRowAt:indexPath:) you have this:
if(indexPath.row == (self.rowCount)) {
//last row, add plus button
}
You can add an else part and remove the plus button again:
if(indexPath.row == (self.rowCount)) {
//last row, add plus button
} else {
//not last row, remove button
}
The Right Way
UITableViewCell has the function prepareForReuse and as the documentation says:
If a UITableViewCell object is reusable—that is, it has a reuse identifier—this method is invoked just before the object is returned from the UITableView method dequeueReusableCell(withIdentifier:)
So, this is where you "reset" your custom table view cell. In your case you remove the plus button.
You already have a custom UITableViewCell it seems, so this should be a small change.
The Footer Way
As #paragon suggests in his comment, you can create a UIView and add that as a tableFooterView to your UITableView.
let footerView = YourFooterViewHere()
tableView.tableFooterView = footerView
Hope that helps