Question

我研究过这个，我很确定这是正确的方法，但我一直在

 fatal error: unexpectedly found nil while unwrapping an Optional value

在prepareForSegue行

上

 selectSingleVC!.delegate = self

相关的代码位在这里。我不确定为什么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)

        }
    })
}

我已经绞尽脑汁待了几个小时，在我的错误中需要一些帮助。感谢

Answer 1

检查selectSingleVC。它崩溃是因为selectSingleVC是nil，您确定它是SelectSingleViewController类型，并尝试使用强制解包!操作。

我的猜测是标识符selectSingleSegue的segue未与故事板中的SelectSingleViewController相关联。请仔细检查您的连接。

Answer 2

@dan segue.destinationViewController提到的

等于UINavigationViewController，因为Swift 2的变化

let selectSingleVC = segue.destinationViewController.topViewController as? SelectSingleViewController

将不再有效。我修改后的代码是

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    if segue.identifier == "messagesChatSegue" {

        let chatVC  = (segue.destinationViewController as! UINavigationController).topViewController as! ChatViewController

        //chatVC.hidesBottomBarWhenPushed = true
        let groupId = sender as! String
        chatVC.groupId = groupId
    } else if segue.identifier == "selectSingleSegue" {
        let selectSingleVC = (segue.destinationViewController as! UINavigationController).topViewController as! SelectSingleViewController
        print(segue.destinationViewController)
        selectSingleVC.delegate = self
    } else if segue.identifier == "selectMultipleSegue" {
        let selectMultipleVC = (segue.destinationViewController as! UINavigationController).topViewController as!SelectMultipleViewController
        selectMultipleVC.delegate = self
    }

}

swift 2.1表视图控制器segue查看委托错误，意外发现nil

2 个答案: