ios - swift 2.1 TableView Controller segue 来查看意外发现 nil 的委托(delegate)错误

Question

我研究过这个，我很确定这是正确的方法，但我不断得到

 fatal error: unexpectedly found nil while unwrapping an Optional value

在prepareForSegue行

 selectSingleVC!.delegate = self

相关的代码位在这里。我不知道为什么 nil 在那里，它让我发疯:-)

class FriendsChatViewController: UITableViewController, UIActionSheetDelegate, SelectSingleViewControllerDelegate, SelectMultipleViewControllerDelegate {

...

@IBAction func compose(sender: UIBarButtonItem) {

weak var wself: FriendsChatViewController? = self

let action = UIAlertController(title: nil, message: nil, preferredStyle: UIAlertControllerStyle.ActionSheet)

let cancelAction = UIAlertAction(title: "Cancel", style: UIAlertActionStyle.Cancel) { _ in
}

let singleAction = UIAlertAction(title: "Single recipient", style: UIAlertActionStyle.Default) { _ in
    if let _ = wself {
        self.performSegueWithIdentifier("selectSingleSegue", sender: self)

    }
}

let multipleAction = UIAlertAction(title: "Multiple recipients", style: UIAlertActionStyle.Default) { _ in
    if let _ = wself {
       self.performSegueWithIdentifier("selectMultipleSegue", sender: self)

    }
}


action.addAction(cancelAction)
action.addAction(singleAction)
action.addAction(multipleAction)

self.presentViewController(action, animated: true, completion: nil)

}

...

    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    if segue.identifier == "messagesChatSegue" {
        let chatVC = segue.destinationViewController as! ChatViewController
        //chatVC.hidesBottomBarWhenPushed = true
        let groupId = sender as! String
        chatVC.groupId = groupId
    } else if segue.identifier == "selectSingleSegue" {
        let selectSingleVC = segue.destinationViewController as? SelectSingleViewController
        print(self)
        selectSingleVC!.delegate = self  <-- ERROR is here
    } else if segue.identifier == "selectMultipleSegue" {
        let selectMultipleVC = segue.destinationViewController as? SelectMultipleViewController
        selectMultipleVC!.delegate = self
    }

}

这是我的 SelectSingleViewController 的相关部分

protocol SelectSingleViewControllerDelegate {
func didSelectSingleUser(user: PFUser)
}

class SelectSingleViewController: UITableViewController, UISearchBarDelegate {

var friends = [PFObject]()
var user = PFUser()
var delegate: SelectSingleViewControllerDelegate!

...

override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
    tableView.deselectRowAtIndexPath(indexPath, animated: true)
    self.dismissViewControllerAnimated(true, completion: { () -> Void in
        if self.delegate != nil {
            let friendObject = self.friends[indexPath.row]
            let friend = friendObject["user"] as! PFUser
            self.user = friend

            print(self.user)
            self.delegate.didSelectSingleUser(self.user)

        }
    })
}

我已经为此绞尽脑汁好几个小时了，需要一些帮助来解决我的错误。谢谢

Answer 1

选中selectSingleVC。它崩溃是因为 selectSingleVC 为 nil 并且您确定它的类型为 SelectSingleViewController 并尝试使用强制解包 !操作。

我的猜测是带有标识符selectSingleSegue的segue没有链接到 Storyboard中的SelectSingleViewController。请仔细检查您的连接。