self.tableView.reloadData() not working in Swift

Question

I\'m attempting to learn Swift & the basics of iOS dev at the same time, so bear with me. I\'ve got a TableViewController that is

Answer 1

All the calls to UI should be asynchronous, anything you change on the UI like updating table or changing text label should be done from main thread. using DispatchQueue.main will add your operation to the queue on the main thread.

Swift 4

DispatchQueue.main.async{
    self.tableView.reloadData()
}

Answer 2

I was also facing the same issue, what I did wrong was that I'd forgot to add

tableView.delegate = self    
tableView.dataSource = self

in the viewDidLoad() {} method. This could be one reason of self.tableView.reloadData() not working.

Answer 3

If your connection is in background thread then you should update UI in main thread like this

self.tblMainTable.performSelectorOnMainThread(Selector("reloadData"), withObject: nil, waitUntilDone: true)

As I have mentioned here

Swift 4:

self.tblMainTable.performSelector(onMainThread: #selector(UICollectionView.reloadData), with: nil, waitUntilDone: true)

Answer 4

You'll need to reload the table on the UI thread via:

//swift 2.3
dispatch_async(dispatch_get_main_queue(), { () -> Void in
    self.tableView.reloadData()
})

//swift 5
DispatchQueue.main.async{
    self.tableView.reloadData()
}

Follow up: An easier alternative to the connection.start() approach is to instead use NSURLConnection.sendAsynchronousRequest(...)

//NSOperationQueue.mainQueue() is the main thread
NSURLConnection.sendAsynchronousRequest(NSURLRequest(URL: url), queue: NSOperationQueue.mainQueue()) { (response, data, error) -> Void in
    //check error
    var jsonError: NSError?
    let json: AnyObject? = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.allZeros, error: &jsonError)
    //check jsonError
    self.collectionView?.reloadData()
}

This doesn't allow you the flexibility of tracking the bytes though, for example you might want to calculate the progress of the download via bytesDownloaded/bytesNeeded