self.tableview.reloaddata() not being called in swift - ios

Question

class NewsTableViewController: UITableViewController {
#IBOutlet weak var authenticationButton: UIBarButtonItem!
var blogPosts = []
override func viewDidLoad() {
super.viewDidLoad()
// Uncomment the following line to preserve selection between presentations
// self.clearsSelectionOnViewWillAppear = false
// Uncomment the following line to display an Edit button in the navigation bar for this view controller.
// self.navigationItem.rightBarButtonItem = self.editButtonItem()
self.navigationItem.title = PFConfig.currentConfig().objectForKey("title") as? String
authenticationButton.enabled = true
if let authEnabled:Bool = PFConfig.currentConfig().objectForKey("adminEnabled") as? Bool {
if authEnabled {
authenticationButton.tintColor = UIView.appearance().tintColor
} else {
authenticationButton.tintColor = UIColor.darkGrayColor()
}
}
loadPosts()
//set the title
PFConfig.getConfigInBackgroundWithBlock { (var config: PFConfig!, var error: NSError!) -> Void in
if error == nil {
if let title:String = config.objectForKey("title") as? String {
self.navigationItem.title = title
}
if let authEnabled:Bool = config.objectForKey("adminEnabled") as? Bool {
if authEnabled {
self.authenticationButton.tintColor = UIView.appearance().tintColor
} else {
self.authenticationButton.tintColor = UIColor.darkGrayColor()
}
}
}
}
}
// MARK: - Table view data source
override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
// #warning Potentially incomplete method implementation.
// Return the number of sections.
return 0
}
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
// #warning Incomplete method implementation.
// Return the number of rows in the section.
return blogPosts.count
}
#IBAction func authenticate(sender: UIBarButtonItem) {
//check if enabled, and if not, get error message from config
if sender.tintColor != UIColor.darkGrayColor() {
//enabled
var authAlert = UIAlertController(title: "Authenticate", message: "Please login to access the admin page.", preferredStyle: UIAlertControllerStyle.Alert)
authAlert.addTextFieldWithConfigurationHandler({(textField: UITextField!) in
textField.placeholder = "Password"
})
authAlert.addAction(UIAlertAction(title: "Cancel", style: UIAlertActionStyle.Cancel, handler: nil))
authAlert.addAction(UIAlertAction(title: "Go", style: UIAlertActionStyle.Default, handler: { (goAction) -> Void in
let textField:UITextField = authAlert.textFields![0] as UITextField
let text = textField.text
self.authenticateUser(text)
}))
self.presentViewController(authAlert, animated: true, completion: nil)
} else {
//disabled
var serverMessage = PFConfig.currentConfig().objectForKey("adminEnabledMessage") as? String
var errorMessage = UIAlertController(title: "Error", message: "The Admin Console is not enabled right now. Message from server: \(serverMessage!)", preferredStyle: UIAlertControllerStyle.Alert)
errorMessage.addAction(UIAlertAction(title: "Dismiss", style: UIAlertActionStyle.Default, handler: nil))
self.presentViewController(errorMessage, animated: true, completion: nil)
}
}
//authHandlers
func authenticateUser(password: String) {
//get the server password
let serverPass = PFConfig.currentConfig().objectForKey("password") as? String
if password == serverPass {
//move them to the admin console
self.performSegueWithIdentifier("showConsole", sender: nil)
} else {
//error message
var errorMessage = UIAlertController(title: "Error", message: "Incorrect password, please try again.", preferredStyle: UIAlertControllerStyle.Alert)
errorMessage.addAction(UIAlertAction(title: "Dismiss", style: UIAlertActionStyle.Default, handler: nil))
self.presentViewController(errorMessage, animated: true, completion: nil)
}
}
func loadPosts() {
let query = PFQuery(className: "Posts")
query.findObjectsInBackgroundWithBlock { (objects, error: NSError!) -> Void in
if error == nil {
self.blogPosts = objects
self.tableView.reloadData()
} else {
var errorMessage = UIAlertController(title: "Error", message: "There was an error retrieving the posts. Please try again later. \(error.localizedDescription)", preferredStyle: UIAlertControllerStyle.Alert)
errorMessage.addAction(UIAlertAction(title: "Dismiss", style: UIAlertActionStyle.Default, handler: nil))
self.presentViewController(errorMessage, animated: true, completion: nil)
}
}
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath) as PostTableViewCell
// Configure the cell...
let currentPost:PFObject = blogPosts.objectAtIndex(indexPath.row) as PFObject
let title = currentPost.objectForKey("title") as String
cell.titleLabelC.text = title
let gmtFormatter:NSDateFormatter = NSDateFormatter()
gmtFormatter.dateFormat = "E MMM d # hh:mm a"
let dateString = gmtFormatter.stringFromDate(currentPost.createdAt)
cell.detailsLabelC.text = dateString
return cell
}
Here is my code for the UITableView that I added to my storyboard. For some reason, when I call self.tableView.reloadData() in loadPosts(), it won't update the table and simply won't call cellForRowAtIndexPath. Any idea why?

Answer 1

Your TableViewDataSource always returns 0 for the number of sections but you need at least 1. Just remove that DataSource function because it is 1 by default.

Answer 2

This error about multithreading.
UITableView - it is UI element. UI works only in main thread. That means that reloadData also works only in main thred.
In your code query.findObjectsInBackgroundWithBlock is async method. So reloadData will not work in this method.
You should call it in main thread through GCD.
dispatch_async(dispatch_get_main_queue(), {
self.tableView.reloadData()
})