删除行时TableView“无法识别的选择器发送到实例”错误

Question

I have a button that deletes the cell it resides within. The data model is working fine and tableView.reloadData() causes no errors. When I use tableView.deleteRowsAtIndexPaths(..) however, a crash occurs that tells me the following:

-[__NSCFNumber row]: unrecognized selector sent to instance 0xb000000000000003
2014-10-29 03:37:08.999 SampleApp[4915:82542] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFNumber row]: unrecognized selector sent to instance 0xb000000000000003'

The code that indicates where this occurs is shown below. I have got a feeling it is related to my Notification, but I don't know why. I tried using nil as the argument for object when posting the notification, but that doesn't make a difference. I don't see why tableView.reloadData() would work, while the alternative method wouldn't. How can I stop this from occurring?

GoalTableViewCell class which inherits from UITableViewCell (excerpt)

@IBAction func deleteButtonTapped(sender: AnyObject) { //IBAction is connected to a delete button within the cell.
        let index = self.indexInTable //indexInTable is an Int property that tracks where the cell is located in the tableView. It is updated using cellForRowAtIndexPath(..)
        var userInfo = ["index" : index]
        NSNotificationCenter.defaultCenter().postNotificationName("DeletedGoal", object: self, userInfo: userInfo)
    }

GoalsTableViewController class which inherits from UIViewController (and has a tableView in it) (excerpt)

    func deletedGoal(notification : NSNotification) {
        if (notification.name == "DeletedGoal") {
            var userInfo = notification.userInfo!
            var index = userInfo["index"] as Int //this is returning the proper index.

            goalsArray.removeAtIndex(index)
            saveGoals(goalsArray)
            //self.tableView.reloadData() //this works.
            self.tableView.deleteRowsAtIndexPaths([index], withRowAnimation: UITableViewRowAnimation.Fade) //this causes error

        }
    }

Edit: I corrected the code (much appreciated guys) but am met with a new error. I may just open a new question for this: After deleting a higher number of cells in a row I eventually get a crash telling me the indexPath is too high. I am guessing cellForRowAtIndexPath(..) is the issue, it does not mark the cell's indexInTable property unless scrolling occurs(?)

    //correct code
   func deletedGoal(notification : NSNotification) {
            if (notification.name == "DeletedGoal") {
                var userInfo = notification.userInfo!
                //var cell = userInfo["cell"] as GoalTableViewCell
            var index = userInfo["index"] as Int

            println(index)
            goalsArray.removeAtIndex(index)
            saveGoals(goalsArray)
            let indexPath = NSIndexPath(forRow:index,inSection:0)
            self.tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: UITableViewRowAnimation.Fade)
            //self.tableView.reloadData()

        }
    }

Answer 1

If you look at the exception message you will see [__NSCFNumber row] which tells you there was an attempt to invoke the row method on an NSCFNumber (which is an internal class for an NSNumber ) - which doesn't have a row method.

Now look at self.tableView.deleteRowsAtIndexPaths([index], withRowAnimation: UITableViewRowAnimation.Fade) - The method name tells you (or you could read the documentation) that it wants an array of NSIndexPath s not NSNumber s

So, what you wanted to say was

self.tableView.deleteRowsAtIndexPaths([NSIndexPath(forRow:index inSection:0)], withRowAnimation:UITableViewRowAnimation.Fade)

This is assuming your table only has one section. If it has more than one section then you will need to keep track of the section number in your cell as well as the row. You could do this by changing the property you store to be the indexPath rather than IndexPath.row .

Then you can say

@IBAction func deleteButtonTapped(sender: AnyObject) { //IBAction is connected to a delete button within the cell.
        let index = self.indexInTable //indexInTable is an NSIndexPath property that tracks where the cell is located in the tableView. It is updated using cellForRowAtIndexPath(..)
        var userInfo = ["index" : index]
        NSNotificationCenter.defaultCenter().postNotificationName("DeletedGoal", object: self, userInfo: userInfo)
    }

func deletedGoal(notification : NSNotification) {
    if (notification.name == "DeletedGoal") {
        var userInfo = notification.userInfo!
        var index = userInfo["index"] as NSIndexPath

        goalsArray.removeAtIndex(index.row)
        saveGoals(goalsArray)
        //self.tableView.reloadData() //this works.
        self.tableView.deleteRowsAtIndexPaths([index], withRowAnimation: UITableViewRowAnimation.Fade) //this causes error

    }
}

Answer 2

The problem is most likely that var index is set to be typeof Int.

However, the methode deleteRowsAtIndexPaths expects an object of type NSIndexPath , since internally it will call the selector row on the passed path.

In your case the selector is called on an Int, which does not respond to the row selector. Create an indexpath with index as your row first and you'll be good to go. :D