Swift - 核心數據運行時錯誤

Question

嘗試在單元格中創建textLabels數組時，出現此運行時錯誤。

我的代碼如下所示：

else { 
     mySelectedCell.accessoryType = UITableViewCellAccessoryType.Checkmark 
     mySelectedCell.tintColor = UIColor.blackColor() 

     if let tx = mySelectedCell.textLabel?.text as Optional?{ 

      var textLabel:String = String()     
      textLabel = tx!     
      var tempFriend = Model(entity: en!, insertIntoManagedObjectContext: context) 

      //Save user to core data     
      tempFriend.tempUser = textLabel 

      //Save context 
      context.save(nil) 

      //Make list from objects 
      liste = context.executeFetchRequest(freq, error: nil)! 

      //Make new list of strings from first list 

      for var i = 0; i < liste.count; ++i{ 

       var data:NSManagedObject = liste[i] as NSManagedObject 
       //The next line is where the error appears 
       showList.append(data.valueForKeyPath("tempUser") as String) 
      } 

      //Show list     
      println(showList) 

      } 
     } 
     } 

我的錯誤說：

fatal error: unexpectedly found nil while unwrapping an Optional value (lldb).

我不明白爲什麼有些會在我的代碼返回"nil"。

任何想法，將不勝感激。

Answer 1

你正在強制展開一個可選值nil。由於您已經省略了錯誤的堆棧跟蹤，因此很難判斷哪一個。試試這個：

else { 
    mySelectedCell.accessoryType = UITableViewCellAccessoryType.Checkmark 
    mySelectedCell.tintColor = UIColor.blackColor() 

    if let textLabel = mySelectedCell.textLabel?.text, 
     let entity = en { 

     var tempFriend = Model(entity: entity, insertIntoManagedObjectContext: context) 

     //Save user to core data     
     tempFriend.tempUser = textLabel 

     //Save context 
     context.save(nil) 

     //Make list from objects 
     liste = context.executeFetchRequest(freq, error: nil)! 

     //Make new list of strings from first list 

     for var i = 0; i < liste.count; ++i{ 

      var data:NSManagedObject = liste[i] as NSManagedObject 
      //The next line is where the error appears 
      showList.append(data.valueForKeyPath("tempUser") as String) 
     } 

     //Show list     
     println(showList) 

     } 
    } 
    }