Ios 索引空缓冲区PFQuery-字符串数组

我对Swift和iOS编程比较陌生，所以我不知道为什么我的字符串不起作用。每当我为字符串的任何索引运行println时，都会得到一个索引空缓冲区错误。这将使用解析并在服务器上查询对象

class ViewController: UIViewController {

 var wordString = [String]()


 func CallData() {
     var query : PFQuery = PFQuery(className: "example class")
     query.whereKey("example type", equalTo: "example category")
     query.findObjectsInBackgroundWithBlock {
         (objects: [AnyObject]!, error: NSError!) -> Void in
         if error == nil {
             println("Successfully retrieved \(objects.count) scores.")
             if let objects = objects as? [PFObject] {
                 for object in objects {
                     self.wordString.append(object["Word"] as String)
                 }
             }
         } else {
             println("Error: \(error) \(error.userInfo!)")
         }
     }
 }



 override func viewDidLoad() {
     super.viewDidLoad()
     CallData()
     println(wordString[0])
 }



 override func didReceiveMemoryWarning() {
     super.didReceiveMemoryWarning()
 }

}

---

如果列未定义或为空，或者客户端试图打印它时将崩溃

let = object["Word"] as String {
   self.wordString.append(newObject)

}     

这基本上是swift的试抓块