Swift - app crashes on TableView UIRefreshControl

Question

When I start to update the table view (pull down to refresh), and then suddenly start flipping list, the application crashes.

fatal error: Cannot index empty buffer

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCellWithIdentifier("BankCell", forIndexPath: indexPath) as BankTableViewCell

    cell.backgroundColor = UIColor(red: 241/255, green: 233/255, blue: 220/255, alpha: 1.0)

    let bank:Bank = self.allRates[indexPath.row] as Bank // <-- Error here

    cell.titleLabel.text = bank.name

    return cell
}

Probably I have to check the existence of an element in the array. But is this the right way out?

- I edit row #2:

let cell = tableView.dequeueReusableCellWithIdentifier("BankCell") as BankTableViewCell

But the error still remains.

My refresh function:

func refresh(sender:AnyObject)
{

    parser.deleteObjects()
    self.allRates.removeAll(keepCapacity: false)

    parser.parse { // - XMLParser ended to Parse file

        self.allRates = self.parser.actualBankRates + self.parser.notActualBankRates

        self.tableView.reloadData()

        self.refreshController.endRefreshing()
    }
}

In XMLParser:

var actualBankRates = [Bank]()
var notActualBankRates = [Bank]()

Answer 1

You forgot to register your class and therefore dequeueReusableCellWithIdentifier:forIndexPath: is unable to return the cell, eg call

tableView.registerClass(BankCell.classForCoder(), forCellReuseIdentifier: "BankCell")

when initializing your table view delegate.

Edit check, that your array allRates is initialized and filled. The error means, that it is empty.

Answer 2

You should ensure that your "allRates" array can be accessed at that index. Write the following code to make sure it won't crash:

if self.allRates.count > indexPath.row
{
    // Ensure you get a valid Bank returned
    if let bank = self.allRates[indexPath.row] as Bank
    {
        cell.titleLabel.text = bank.name
    }
}

You could then debug it by sticking a breakpoint on the first if statement and typing po self.allRates to check the state of your array before you tried accessing it.