Label takes a couple of seconds to unhide - iphone

Question

So I recently started using Swift and basically I have a UILabel I use to display error messages. This label is intially hidden (through storyboard's hidden checkmark, I tried setting it to hidden in viewDidLoad also).
When a user clicks login an apicontroller class posts to a backend server to check credentials. The apicontroller has a delegate which is called in the completionHandler in (NSURLSession.dataTaskWithRequest). The protocol method in the viewcontroller checks to see the http status and if it's 200 it moves on to the next view. However, if it's not 200, the view controller unhides the error label
(self.errorLabel.hidden = false and self.erorLabel.text = "ERROR MESSAGE HERE").
Here is my issue:
When the erorrlabel is supposed to be unhidden, I set it's hidden property to false, println("should be unhidden now") and display an alert. The alert and print statement are executed instantly. However, the label takes a couple of seconds before it is displayed.
I've tried this on the 4s, 5, 5s and 6 in simulator and an actual 5s and I still get this issue. I've also tried manually refreshing the view with self.view.setNeedsDisplay() and it still doesn't work.
Any ideas?

Answer 1

You are probably updating the label in a thread which is not the main thread.
Enclose the code inside this block:
dispatch_async(dispatch_get_main_queue()) {
// Update the label here
}

Answer 2

Thanks to Antonio for reffering me to this question. It has indeed resolved my problem which I asked here: https://stackoverflow.com/questions/26800093/setting-iboutlet-in-closure-result-in-swift
This is the final block of code which worked for me:
homeModel.GetHomeData({(textResult:String!) in
dispatch_async(dispatch_get_main_queue())
{
// Update the textview in the ui here
self.homeTextView.text = textResult
}
});