showing a double value in a custom cell in uitableview-CodePudding

So, full disclosure: I'm a newbie to Swift.

I'm working on an app, trying to get a label in a custom cell to display a DOUBLE value. I've tried to do an if let conditional binding to cast it from a string to a double, but my source isn't an optional type, and I can't make it optional. So I'm not sure how to do this.

Here are the specific errors:
initializer for conditional binding must have Optional type, not 'Double'
Cannot assign value of type 'Double?' to type 'String?'
No exact matches in call to initializer

and here's the code:

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "DemoTableViewCell", for: indexPath) as! DemoTableViewCell
        
        cell.partNameLabel.text = parts[indexPath.row].partName
        
        // Convert string value to double
        if let value = parts[indexPath.row].partCost {
             cell.partCostLabel.text = Double(value)
        } else {
            cell.partCostLabel.text = 0.00
        }
        cell.purchaseDateLabel.text = parts[indexPath.row].purchaseDate

        return cell
    }

Thanks in advance!

CodePudding user response：

you tried to assign double to string, in here you need the conversion of double (yourvalue) to string(cell.partCostLabel.text) using String(format:), foe e.g,

initializer for conditional binding must have Optional type, not 'Double' Cannot assign value of type 'Double?' to type 'String?' No exact matches in call to initializer

Ans :

     cell.partCostLabel.text = "0.00"
     if let value = parts[indexPath.row].partCost {
       cell.partCostLabel.text = String(format: "%.2f", Double(value))
      }

for more info : Swift double to string

CodePudding user response：

From the error, it looks like parts[indexPath.row].partCost is already a Double -- the error is telling you if let only works with Optional types.

So, you can replace your if let / else block with:

cell.partCostLabel.text = String(format: "%.2f", parts[indexPath.row].partCost)

cell.partCostLabel.text = 0.00 doesn't work because Text expects a String -- you won't need this anymore with the above code, but the way to handle it would be cell.partCostLabel.text = "0.00"

Finally, Cannot assign value of type 'Double?' to type 'String?' -- I'm not sure what line that's occurring on, but if it's cell.purchaseDateLabel.text = parts[indexPath.row].purchaseDate then that means that purchaseDate is a Double? and you're trying to set it to something that expects a String. You will need to consider how you're going to convert a Double to a date, but this one might be the one where you need if let:

if let purchaseDate = parts[indexPath.row].purchaseDate {
  cell.purchaseDateLabel.text = "\(purchaseDate)" //you probably want a different way to display this, though
}