预期返回'UITableViewCell的函数中缺少返回

Question

Why Do I get this error? Switch statement doesn't return cell? Can somebody explain this?

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

    switch indexPath.row {
    case 0:
        let cell = tableView.dequeueReusableCell(withIdentifier: "LogoStyle1", for: indexPath) as! LogoStyle1
        cell.backgroundColor = UIColor.clear
        return cell
    case 1:
        let cell = tableView.dequeueReusableCell(withIdentifier: "FieldStyle1", for: indexPath) as! FieldStyle1
        cell.backgroundColor = UIColor.clear
        cell.delegate = self
        return cell
    case 2:
        let cell = tableView.dequeueReusableCell(withIdentifier: "ButtonStyle1", for: indexPath) as! ButtonStyle1
        cell.backgroundColor = UIColor.clear
        cell.delegate = self
        return cell
    default:
        break
    }
}

Answer 1

This is one of those things that the compiler gets over-worried about. The compiler is basically asking you, what if indexPath.row is neither 0 nor 1 nor 2? What to return in that case. As the programmer you know that indexPath.row will always be one of those values, but the compiler doesn't know that.

So you need to return something in the default case, but it does not make sense to return anything, does it? In this case, I would just write:

fatalError("Somehow indexPath.row is an unexpected value.")

This will crash the app if the default case is ever reached. If the default case is ever reached, it probably means there is something wrong with your code (or maybe a bug in the API (unlikely)!), because as you know the table view only has 3 rows. The app should probably crash at this point.

Answer 2

CellForRowAtIndexPath delegate method return cell even when the numberOfRowsInSection is 0. So in default block of swicth you need to return a cell. and error will be gone.