從用戶分析對象

Question

在集合視圖中，我有一個事件數組，每個單元格都有一個保存爲PFFile的事件圖像的背景圖像視圖。這工作正常，直到我添加此代碼。用戶有一個屬性「profilePicture」，我也想在單元格中顯示。這是我的代碼，它是在獲取事件圖像的塊內部。

let eventCreator : PFUser = event?.objectForKey("user") as! PFUser 
let creatorImage : PFFile = eventCreator.objectForKey("profilePicture") as! PFFile 
creatorImage.getDataInBackgroundWithBlock({ (data, error) -> Void in 

    cell.creatorImageView.image = UIImage(data: data!) 

}) 

這裏是一個得到該事件的完整的方法和它的所有屬性（比如我說，工作完全正常之前，我加入了上面的代碼現在，它拋出一個「致命錯誤：意外發現零而展開的可選值」的錯誤。任何幫助嗎？

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell { 

    //sets up cell 

    let cell : EventCell = collectionView.dequeueReusableCellWithReuseIdentifier("cell", forIndexPath: indexPath) as! EventCell 

    //adds attend action 

    cell.attendButton.addTarget(self, action: "buttonTapped:", forControlEvents: UIControlEvents.TouchUpInside) 

    //queries parse for events 

    let event = events?[indexPath.row] 

    event?.eventImage.getDataInBackgroundWithBlock({ (data, error) -> Void in 

     if let data = data, image = UIImage(data: data) { 

      if cell.isFlipped == false { 

      cell.eventBackgroundImage.image = image 
      cell.eventTitleLabel.text = event?.eventTitle 

      //gets profile picture of events creator 

      let eventCreator : PFUser = event?.objectForKey("user") as! PFUser 
      let creatorImage : PFFile = eventCreator.objectForKey("profilePicture") as! PFFile 
      creatorImage.getDataInBackgroundWithBlock({ (data, error) -> Void in 

       cell.creatorImageView.image = UIImage(data: data!) 

      }) 

      //sets correct category for cell image 

       if event?.category == "" { 
        cell.categoryImageView.image = nil 
       } 

       if event?.category == "The Arts" { 
        cell.categoryImageView.image = UIImage(named: "University") 
       } 

       if event?.category == "The Outdoors" { 
        cell.categoryImageView.image = UIImage(named: "Landscape") 
       } 

       //TODO finish categories 

      } 

      else if cell.isFlipped == true { 

       cell.eventDescriptionLabel.text = event?.eventDescription 
      } 
     } 
    }) 

Answer 1

你爲什麼要使用as!運營商強行鑄造零值可選變量的非可選一個會導致運行時錯誤？你或許應該使用as?操作相反，並檢查任何nil值，以確保演員成功做任何事情。

[編輯] 嘗試這樣：

if let eventCreator = event?.objectForKey("user") as? PFUser { 
    if let creatorImage = eventCreator.objectForKey("profilePicture") as? PFFile { 
     creatorImage.getDataInBackgroundWithBlock({ (data, error) -> Void in 

      cell.creatorImageView.image = UIImage(data: data!) 

     }) 
    } 
}