IOS/Swift：致命錯誤：意外地發現零，同時展開一個可選值？

Question

func fetchAndReload(){ 
      var error: NSError? 
      let results = coreDataStack.context.executeFetchRequest(fetchRequest, error: &error) as! [Venue]? 
    //fatal error: unexpectedly found nil while unwrapping an Optional value 
if let vs = results { 
      venues = vs 
     } else { 
      println("\(error),\(error?.userInfo)") 
     } 
     self.tableView.reloadData() 
    } 

//我不知道如何處理這個問題。

Answer 1

從文檔：

Write an optional binding for an if statement as follows:

if let constantName = someOptional { 
    statements 
} 

不像你的代碼

let constantName = someOptional 
if let cn = constantName { 
    statements 
} 

...