Question

即使我在使用该值之前检查nil，我也会收到意外发现的nil错误。我在这里错过了什么吗？

if self.orders[indexPath.row]["distanceToHouseHold"] != nil {
    cell.distanceTextField.text = "\(self.orders[indexPath.row]["distanceToHouseHold"] as! String)m"
}

错误在第二行当然。

Answer 1

可能distanceToHouseHold不是字符串，并且在类型转换时失败。尝试使用if-let检查或新的guard检查。

if let distance = self.orders[indexPath.row]["distanceToHouseHold"] as? String {
    cell.distanceTextField.text = "\(distance)m"
}

Answer 2

请改为：

if let distance self.orders[indexPath.row]["distanceToHouseHold"] as? String {
    cell.distanceTextField.text = distance + "m"
}

这将检查它不是n并且转换为字符串

Answer 3

使用guard let

guard let whatever = self.orders[indexPath.row]["distanceToHouseHold"] as? String else  {
  return 
} 
    cell.distanceTextField.text = whatever + "m"
}

如果不能正常工作，请尝试：

guard let whatever = self.orders[indexPath.row]["distanceToHouseHold"] else  {
      return 
    } 
        cell.distanceTextField.text = String(whatever) + "m"
}

Answer 4

试试这个：

let whatValue = self.orders[indexPath.row]["distanceToHouseHold"]
println(" value is \(whatValue)");

这将帮助您查看输出内容。之后你可以决定出了什么问题。

干杯!!

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4 个答案: