ios - UILabel 在展开可选值 Swift 3 时意外发现 nil 设置文本

Question

在我的自定义 collectionview 单元格中，我有

@IBOutlet weak var boardNameLabel: UILabel!

var boardInfoDic: Dictionary? = [String : AnyObject]() 

func updateItemAtIndexPath(_ indexPath: NSIndexPath) {

    if let string = boardInfoDic?["description"]
        {
            boardNameLabel.text = String(format: "%@", string as! String)
        }
}

我从collectionView cellForItemAt indexPath:as向 boardInfoDic 发送数据

let boardsCollectionViewCell = collectionView.dequeueReusableCell(withReuseIdentifier: KBoardsCollectionViewCellIdentifier, for: indexPath) as! BoardsCollectionViewCell
boardsCollectionViewCell.boardInfoDic = self.boardsDataArray?[indexPath.item] as Dictionary<String, AnyObject>?
boardsCollectionViewCell.updateItemAtIndexPath(indexPath as NSIndexPath)

但我得到了fatal error: unexpectedly found nil while unwrapping an Optional value，我尝试了多种方式但没有用。我该如何解决这个问题？

与 UICollectionViewCell 的插座连接

Answer 1

尝试可选转换

if let string = boardInfoDic?["description"] as? String {
    boardNameLabel.text = String(format: "%@", string)
}

Answer 2

首先确认您的 boardInfoDic 不为空。用这个

    func updateItemAtIndexPath(_ indexPath: NSIndexPath) {

                print(boardInfoDic)
                boardNameLabel.text = String(self.boardInfoDic["description"]!)   

}

Answer 3

这对我有用

if let string = boardInfoDic?["description"] as? String
    {
        boardNameLabel?.text = string
    }

Answer 4

当您这样做时if let string = boardInfoDic?["description"] ，该变量string不是类型String，而是类型AnyObject。结果，当您string转换为 aString时，无法将此类型转换为类型，结果返回 nil。为了从字典中获取字符串，您需要使用 type 来访问它AnyObject。例如

if let string = boardInfoDic?["description"]
        {
            boardNameLabel.text = String(format: "%@", string as! String)
        }  

如果对您有帮助，请务必将其标记为答案。