Downcast from'[NSIndexPath]？'到'[NSIndexPath]'只打開optionals;你的意思是使用'！'嗎？

Question

func backBtnAction(){ 

    var index = collectionView?.indexPathsForSelectedItems() as! [NSIndexPath] 
    collectionView?.scrollEnabled = true 
    collectionView?.reloadItemsAtIndexPaths(index) 
} 

如何在collectionview得到indexpath ......就像我現在這樣

var index = collectionView?.indexPathsForSelectedItems() as! [NSIndexPath] 

Answer 1

indexPathsForSelectedItems()回報[NSIndexPath]?所以通常的方式是可選的結合，而不鑄造

func backBtnAction() 
{ 
    if let indexes = collectionView?.indexPathsForSelectedItems() { 
     collectionView!.scrollEnabled = true 
     collectionView!.reloadItemsAtIndexPaths(indexes) 
    } 
}