Swift Tableview reusable cell issue - swift

Question

I am having an issue with what I think is reusable cells in a tableview cell, unfortunately I can't work out how to force the state of the cell. I am fairly sure this is the issue because when I reload the tableview everything is displayed correctly. It's only when I scroll that I start to see issues, if I once again reload the display corrects itself.
This is the correct display :
and the incorrect display after scrolling about :
my cellForRowAt code :
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "historyGoalCell", for: indexPath)
let name = items[indexPath.section][indexPath.row].name
let date = dateManager.dateAsString(for: items[indexPath.section][indexPath.row].date!)
if tempDate != date {
// show header
cell.textLabel?.text = date
tempDate = date
} else {
// don't show header
cell.textLabel?.text = ""
}
cell.detailTextLabel?.text = "\(date),\(name ?? "")"
return cell
}
Thanks for any help, I have been stuck with this for a couple of days, very new to TableViews - thanks

Answer 1

tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell
can be invoked in any order. It isn't called consistently from 1 to N, so logic with tempDate works not as planned. Better do some pre-work and make an array with indexes where you place headers. For example
struct Pair : Hashable {
var i : Int
var j : Int
}
//Somewhere one time before the first reloadData
var hasIndex : Set<Pair> = []
var tempDate: Date = Date.distantPast
for i in 0..<sections {
for j in 0..<rows[i] {
let name = items[i][j].name
let date = dateManager.dateAsString(for: items[i][j].date!)
if tempDate != date {
hasIndex.insert(Pair(i: i, j: j))
// OR items[i][j].showHeader = true
tempDate = date
} else {
// OR items[i][j].showHeader = false
}
}
}
...
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "historyGoalCell", for: indexPath)
let name = items[indexPath.section][indexPath.row].name
let date = dateManager.dateAsString(for: items[indexPath.section][indexPath.row].date!)
if hasIndex.contains(Pair(i: indexPath.section, j: indexPath.row)) {
// OR if items[indexPath.section][indexPath.row].showHeader {
cell.textLabel?.text = date
tempDate = date
} else {
cell.textLabel?.text = ""
}
cell.detailTextLabel?.text = "\(date),\(name ?? "")"
return cell
}