Ios 在prepareForSegue与swift_dynamicCast发生碰撞

首先，这是我的代码：

let flickerFetcher : FlickrFetcher = FlickrFetcher()

var photos : UIImage[]? = UIImage[]() {
    didSet { self.appsTableView.reloadData() }
}

func prepareImageViewController(ivc: ImageViewController, toDisplayPhoto photo: NSDictionary)
{
    ivc.imageURL = flickerFetcher.URLforPhoto(photo, format: FlickrFetcher.FlickrPhotoFormat.Large)
    ivc.title = photo.valueForKeyPath(flickerFetcher.FLICKR_PHOTO_TITLE) as String
}

// In a storyboard-based application, you will often want to do a little preparation before navigation
override func prepareForSegue(segue: UIStoryboardSegue!, sender: AnyObject!) {
    // Get the new view controller using [segue destinationViewController].
    // Pass the selected object to the new view controller.
 //   NSLog("Prepare for Segue beginning")
    if sender!.isKindOfClass(UITableViewCell) {
      //  NSLog("Sender is UITableViewCell")
        var indexPath : NSIndexPath = self.tableView.indexPathForCell(sender as UITableViewCell)
        if indexPath != nil {
          //  NSLog("IndexPath is nil")
            if segue!.identifier == "Display Photo"{
               // NSLog("Segue Identified")
                if segue!.destinationViewController.isKindOfClass(ImageViewController) {
                    NSLog("DestinationViewController is ImageViewController")
                    var destinationController = segue.destinationViewController as ImageViewController
                    if let photoDict = self.photos?[indexPath.row] as? NSDictionary {
                        self.prepareImageViewController(destinationController, toDisplayPhoto:photoDict)
                    }

                }
            }
        }
    }

}

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我已经将问题缩小到了最后一行中prepareImageViewController的实现，它给了我一个链接到swift_dynamicCast的崩溃。我似乎不明白

在使用之前，请确保您的照片字典是正确的

if let photoDict = self.photos?[indexPath.row] as? NSDictionary {
    self.prepareImageViewController(destinationController, toDisplayPhoto:photoDict)
}

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伴随崩溃的错误是什么？如果没有，您是否尝试过跟踪？它是

线程1:EXC\u断点（code=EXC\u I386\u BPT，subcode=0x0）

谢谢Connor，我本来就有这个，但在我试图找出错误的时候把它取出来了。还是有错误，是的，非常一样。这个看起来对吗

func-URLforPhoto（photo:NSDictionary，format:FlickrPhotoFormat）->NSURL{return-NSURL（coder:self.urlStringForPhoto（photo，format:format）as-NSCoder）}

我试过了，不再出现错误，但似乎照片仍然没有打开。当segue发生时，它应该打开照片，照片的名称应该是新视图控制器的标题。标题现在正在显示，但照片没有显示