dequeueReusableCellWithIdentifier creating a new cell instead of reusing one - ios

Question

I use a UITableView inside a UIViewController with custom cells. However, when dequeueReusableCellWithIdentifier is called, it sometimes creates a new cell instead of reusing an existing one.
For example: When the first cell gets updated for the first time, a new cell is created instead of reusing the original cell.
I have created a diagram to help better illustrate the problem. Each green rectangle is an action that should happen, and each red rectangle is one that shouldn't. Each arrow is a call of dequeueReusableCellWithIdentifier.
It's problematic when a UIButton is tapped (the action is called multiple times), and with a "swipe to delete" action, the cell which has been swiped can be covered by the new second cell, which makes it appear like the delete button is randomly disappearing.
How can I solve this problem?
EDIT:
code custom cell
class TableViewCell : UITableViewCell{
#IBOutlet weak var buttonStop: UIButton!
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
print("newCell")
backgroundColor = color
}
override init(style: UITableViewCellStyle, reuseIdentifier: String?) {
super.init(style: style, reuseIdentifier: reuseIdentifier)
}
override func prepareForReuse() {
super.prepareForReuse()
}
var color = UIColor().randomColor()
}
code for extension randomColor
extension UIColor {
func randomColor() -> UIColor {
let aRedValue = CGFloat(arc4random()) % 255 / 255
let aGreenValue = CGFloat(arc4random()) % 255 / 255
let aBlueValue = CGFloat(arc4random()) % 255 / 255
return UIColor(red: aRedValue, green: aGreenValue, blue: aBlueValue, alpha: 1)
}
code for cellForRow
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell
{
let cell = tableView.dequeueReusableCellWithIdentifier("Cell",forIndexPath: indexPath) as! TableViewCell
cell.buttonStop.tag = indexPath.row
cell.buttonStop.addTarget(self, action: "buttonAction:", forControlEvents: UIControlEvents.TouchUpInside)
return cell
}
buttonAction:
func buttonAction(sender: UIButton) {
print("action for cell : \(sender.tag)")
}
I reduced the code to the max , note after further investigation the button printed the same text because of one of my mistake I write the message twice ^^'
So the only problem remaining is for the "swipe to delete" gesture

Answer 1

If I understand correctly you have a problem with keeping (the result of) an action in sync with what is displayed in the tableView.
Understand how UITableView uses the cells: it will ask it's dataSource for a UITableViewCell. You can either create one every time, or ask the tableView for one to reuse. Because of this mechanism, a cell you create can appear in a certain position at one time, and another position later.
Make sure that your logic and data is independent of the actual tableViewCells at all times. So you should be able to do what you have to o with ONLY an NSIndexPath.
A UITableViewCell can give you a valid indexPath for a tableViewCell via one of two method -indexPathForCell: or indexPathForRowAtPoint:.
The way to handle actions on UITableViewCells is as follows:
Create a custom subclass of UITableViewCell
Create a protocol in this subclass (e.g. MyCellDelegate)
Give this class a property delegate of type id <MyCellDelegte>
When creating a cell in your dataSource, sign this dataSource to be the delegate of that cell.
Let this subclass handle the action (swipe / tap) by calling a method from your protocol on it's delegate (the delegate is your datasource).
In the implementation of that delegate method (on your datasource) you can call one of the methods on UITableView to get the indexPath. This is the point where you become independent on the actual tabelViewCell: use that indexPath to get data, or perform a certain operation.
Although this might seem like a lot of work for a small thing, it really is not that much work, and your code will be much more robust, easier to follow and less coupled.