reloadData() 不更新单元格标签

Question

In my app I have a label that inform the user that a few settings are missing:

which is set in:

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let service = (fetchedResultsController?.object(at: indexPath))! as Service
    let cell = tableView.dequeueReusableCell(withIdentifier: cellId, for: indexPath) as! OfferedServiceCell
    cell.setupDataCell(service: service)
    if service.employee?.count == 0   || service.price?.price == nil || service.price?.slotDuration == nil {
        cell.infoLabel.text = "attention: you need to complete this service set up!"
    }
    let lpGestureRecognizer: UILongPressGestureRecognizer = UILongPressGestureRecognizer(target: self, action: #selector(didLongPressCell(gr:)))
    cell.addGestureRecognizer(lpGestureRecognizer)
    return cell
}

User can add price and employee proving that service in another tableViewController and the label should go away when all the information needed are saved in core data. The problem is that the label red warning goes away only when I reload the viewController.

THIS IS WHAT I HAVE TRIED SO FAR:

1. Since I am using fetchedResultsController, I have implemented this method:

    func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) { DispatchQueue.main.async { self.tableView.reloadData() } }

   The method gets called as soon as I change core data but the warning is still there (unless the TableViewController is reloaded). I have also tried to add self.tableView.layoutIfNeeded() and infoLabel.layoutIfNeeded() in OfferedServiceCell .

2. Post a notification when the TableViewController where I add price and employee is dismissed:

    NotificationCenter.default.addObserver(self, selector: #selector(reloadAllData), name: NSNotification.Name(rawValue: "priceListModified"), object: nil)

in reloadAllData I even tried to call performFetch again

func reloadAllData(){
     DispatchQueue.main.async {
                do {
                    try self.fetchedResultsController?.performFetch()

                } catch {
                    fatalError("Failed to initialize FetchedResultsController: \(error)")
               }

        self.tableView.reloadData()
        self.tableView.layoutIfNeeded()
        }
}

I don't know what else I can do. Thanks for you suggestions.

-----UPDATE--- problem solved:

As correctly pointed out by Chris Trahey's answer I ended up moving the code where I set up the red label to my custom cell and explicitly hide it when it isn't needed:

func setupDataCell(service:Service){
    self.service =  service
    if service.service_description != nil {
        serviceName.text = service.service_description
    }

    if service.employee?.count == 0   || service.price?.price == nil || service.price?.slotDuration == nil {
        if service.selected == 0 {
        infoLabel.text = "Drag service to Service Offered to start using it"
        }else{
        infoLabel.text = "attention: you need to complete this service set up!"
        }
    }else{
        infoLabel.isHidden = true
    }
}

and I used prepareForReuse to set the label to nil. (still not sure about this but it doesn't work without)

override func prepareForReuse() {
    super.prepareForReuse()
    infoLabel.text = nil

}

Answer 1

I suspect that the cell setup routine is not clearing out the label in the event that it is not required. Therefore, the label is surviving the re-use cycle. I would do both of:

• setupDataCell should not just set the red label properties when it's needed, it should also explicitly hide it when it isn't.
• implement prepareForReuse on the custom cell class and clear the label