If-statement not working in Swift 3

Basically, I wanted the text from the UIAlertController and use that to filter my table view.

I've just tried to do if-statement, but to no avail. I did the filtering at cellForRowAt:

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "GPAcell", for: indexPath)

    // Configure the cell...
    if let cell = cell.textLabel{
        if (indexPath.section == 0){
            let keys = dc.NUS.keys.sorted()
            let userGPA = DataController.sharedInstance.userInput
            let key = keys[indexPath.row]
            let value = dc.NUS[key]

            if let valuegpa = value{
                if valuegpa.isLessThanOrEqualTo(userGPA) {

                    cell.text = "\(valuegpa)"
                }
                else {
                    cell.text = "no"
                }
            }


    return cell
}

Any suggestions on what I should try to do? Any help is very much appreciated.