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iOS Build a Self-Destructing Message iPhone App Relating Users in Parse.com Adding the Edit Friends Screen

Roderick Kar
Roderick Kar
8,456 Points
Posted by Roderick Kar
Roderick Kar
8,456 Points

fatal error with numberOfRowsInSection written in Swift

i am trying to follow the lesson using Swift. i got a "fatal error: unexpectedly found nil while unwrapping an Optional value" for "let count". i am certain self.allUsers!.count is getting returning a value inside videDidLoad() but i think the way i am doing now in numberOfRowsInSection function to return the same value as integer is incorrect. I would be most grateful if help can be provided.

Thanks.

class EditFriendsViewController: UITableViewController{

var allUsers : [PFUser]?

override func viewDidLoad() {
    super.viewDidLoad()

    var query = PFUser.query()
    query.orderByAscending("username")
    query.findObjectsInBackgroundWithBlock {
        (objects: [AnyObject]!, error: NSError!) -> Void in
        if error == nil {

            self.allUsers = objects as? [PFUser]

            println("Successfully retrieved \(self.allUsers!.count) users.")

            self.tableView.reloadData()

        } else {
            println("Error: \(error.userInfo)")
        }
    }
}

override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
    return 1
}

override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    let count = self.allUsers!.count as Int
    return (count)
}

override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    let row = indexPath.row
    let cell = tableView.dequeueReusableCellWithIdentifier("cell", forIndexPath: indexPath) as UITableViewCell
    let user = self.allUsers![row]
    cell.textLabel!.text! = "Hello"

    return cell
}

}

2 Answers

Stone Preston
Stone Preston
42,016 Points
Stone Preston
Stone Preston
42,016 Points

your allUsers variable is probably nil at first until the network request comes back and it gets set. So when the tableView first appears allUsers is nil, and you are explicitly unwrapping it (basically saying, I know this is not nil so go ahead and use it) and getting this error. you probably need to actually unwrap it and return the count if its not nil, and return some other number if it is nil. 

override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        if let count = self.allUsers?.count as Int {
            return (count)
       } else {
            //allUsers is nil, so just return 0
            return 0
         }

    }

then whenever you get your allUsers back from parse, you reload the tableView which will cause the delegate methods to get called again and this time around it wont be nil, so it will actually return the count of the users

Roderick Kar
Roderick Kar
8,456 Points
Roderick Kar
Roderick Kar
8,456 Points

Hello Stone,

Thanks a lot for your help and suggestion. It makes a lot of sense and it's working now. Just a note, apparently my original code of downcasting allUsers.count as Int generates an error if used as a condition, removing the downcast solves the problem. I can move on to the rest of the lessons.

Many thanks again!

Regards,

Rod

Chris Bracewell
Chris Bracewell
34 Points
Chris Bracewell
Chris Bracewell
34 Points

Hi Stone, how would you convert the text that sets the cell label to the username into Swift? The way that is used in the tutorial is:

pfuser *user = [self.allusers objectAtIndex:indexPath.row];
celll.textlabel.text = user.username;

Any help would be great, thanks

Chris Bracewell
Chris Bracewell
34 Points
Chris Bracewell
Chris Bracewell
34 Points

Roderick, how did you get the username of each object to print to each table cell? I'm covering it to Swift too and can't seem to find a way of doing it.

Any help would be great.

The code snippet is: pfuser *user = [self.allusers objectAtIndex:indexPath.row]; celll.textlabel.text = user.username;