UITableView Swift questions

Question

I want to query using Parse to add strings to an array. Then I want to put those strings into the cells of my UITableView. However, every time I run the app nothing seems to appear on my table. Here is my code if someone could help explain some of the reasons that it may not be appearing

class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate  {

@IBOutlet weak var tableView: UITableView!


var friendsArray: [String] = []

override func viewDidLoad() {
    super.viewDidLoad()
    self.tableView.registerClass(UITableViewCell.self, forCellReuseIdentifier: "cell")

    var usrname = currentUser?.username
    var query = PFQuery(className:"Relation")
    query.whereKey("Sender", equalTo : usrname!)
    query.findObjectsInBackgroundWithBlock {
        (objects: [AnyObject]?, error: NSError?) -> Void in

        if error == nil {
            // The find succeeded.
            //println("Successfully retrieved \(objects) scores.")
            // Do something with the found objects
            if let objects = objects as? [PFObject] {
                for object in objects {
                    var friendName = object["Friend"] as! String
                    println(friendName)
                    self.friendsArray.append(friendName)
                }
            }
        }
        else {
            // Log details of the failure
            println("Error: \(error!) \(error!.userInfo!)")
        }
    }


}


func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return friendsArray.count
}

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {

    var cell:UITableViewCell = self.tableView.dequeueReusableCellWithIdentifier("Cell") as! UITableViewCell

    cell.textLabel?.text = self.friendsArray[indexPath.row]

    return cell
}

func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {

}

Answer 1

You need to call [self.tableView reloadData]; in the completion block of the findObjectsInBackground: call.

Answer 2

When you call findObjectsInBackgroundWithBlock its doing exactly what it name says, specifically its running in the background.

Meanwhile while its running in the background your table view code continues to run in the foreground, effectively in parallel.

So your viewDidLoad function will exit and numberOfRowsInSection will be called next, but at that time if findObjectsInBackgroundWithBlock has not yet finished then friendsArray.count will be 0.

Answer 3

The app does not know when your data will be returned so that you have to explicitly to refresh the UITableView once you have successfully received the data. Use [self.tableView reloadData] to reload the UITableView later on.

The UITableView will only load once when UIViewController gets loaded. Unless, you have already have data the time when UIViewController loads. Otherwise, the number of rows will be 0 at the first time and the delegate method cellForRowAtIndexPath will not be called.

findObjectsInBackgroundWithBlock is an async call when you take a look at the documentation. It's not like its literal meaning that it's running in the background. It means that it won't block the current thread so that users can still have interaction with the application.

Answer 4

At the end of your if error == nil{...} statement, load your table data like this:

if error == nil{
  //All that other stuff...
  tableView.reloadData()
}

Also make sure your tableView has its delegate and datasource connected to your view controller. This may require putting this in viewDidLoad:

tableView.delegate = self
tableView.datasource = self

I also find it peculiar that your tableView is declared as weak, but that may not be relevant.

Try these things and let us know if you're still having trouble. Good luck! :)

Answer 5

just try these things. it will help you after you get array of element make reload the uitableView. if you use storyboard check the datasource outlet it you did not use storyboard or xib, then you set datasource in coding wisse

Answer 6

hi you can use like this

public func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell

{


    let cell : UITableViewCell = tableView.dequeueReusableCell(withIdentifier: "cell")! as UITableViewCell


    cell.textLabel?.text = app.str[indexPath.row]




     print(" cell \(cell.textLabel?.text!)")


    return cell


}

TableOutLet.reloadData()

Answer 7

• Conform your tableView to its delegate and datasource by written below two lines in your viewDidLoad() after super.viewDidLoad():

  tableView.datasource = self tableView.delegate = self

• Then update this code as below :

  if let objects = objects as? [PFObject] { for object in objects { var friendName = object["Friend"] as! String println(friendName) self.friendsArray.append(friendName) } tableView.reloadData() }

• After that in tableView delegate methods return self.friendsArray.count for numberOfRows() method and also put your code in cellForRow also.

Answer 8

Just place your line after appending elements in array.

override func viewDidLoad() {
super.viewDidLoad()


var usrname = currentUser?.username
var query = PFQuery(className:"Relation")
query.whereKey("Sender", equalTo : usrname!)
query.findObjectsInBackgroundWithBlock {
    (objects: [AnyObject]?, error: NSError?) -> Void in

    if error == nil {
        // The find succeeded.
        //println("Successfully retrieved \(objects) scores.")
        // Do something with the found objects
        if let objects = objects as? [PFObject] {
            for object in objects {
                var friendName = object["Friend"] as! String
                println(friendName)
                self.friendsArray.append(friendName)
            }
        }
    }
    else {
        // Log details of the failure
        println("Error: \(error!) \(error!.userInfo!)")
    }
}
self.tableView.registerClass(UITableViewCell.self, forCellReuseIdentifier: "cell")
}

Or you can reload table once your final array up-to-date

Answer 9

As mentionded by another hint you need to call reloadData but you need to call it in main thread to see result as soon as possible

dispatch_async(dispatch_get_main_queue()) {self.tableView.reloadData()}