How to make UIProgressView work in swift - ios

Question

I am trying to implement the UIProgressView!. I am downloading some data from a website and I am not wrapping my head around some of the fundamentals of how to write this code. I have the label called message which will be updated when the data is downloaded, but I want to show the progress of the data being downloaded.
import UIKit
class ViewController: UIViewController {
//They user types in the city they want to recieve the weather from
#IBOutlet weak var city: UITextField!
//The label that is being updated when the data finally reaches the phone
#IBOutlet weak var message: UILabel!
//The progress bar
#IBOutlet weak var downloadProgress: UIProgressView!
//My 'What's the weather?' button
#IBAction func buttonPressed(sender: AnyObject) {
//When you touch the button, the keyboard goes away
self.view.endEditing(true)
//setting the urlString to the address of the website, it will add the city that you type into the city text field
var urlString = "http://www.weather-forecast.com/locations/" + city.text.stringByReplacingOccurrencesOfString(" ", withString: "") + "/forecasts/latest"
//Setting the url to the urlString
var url = NSURL(string: urlString)
let task = NSURLSession.sharedSession().dataTaskWithURL(url!){(data, response, error) in
var urlContent = NSString(data: data, encoding: NSUTF8StringEncoding)
var contentArray = urlContent!.componentsSeparatedByString("<span class=\"phrase\">")
var newContentArray = contentArray[1].componentsSeparatedByString("</span>")
//Updating the message text with the content that I want from the HTML source
self.message.text = (newContentArray[0] as! String)
}
task.resume()
}
override func viewDidLoad() {
super.viewDidLoad()
self.downloadProgress.progress = 0.0
}
func makeMyProgressBarMoving {
var recievedData : Float
var expectedTotalSize : Float
var actual : Float = downloadProgress.progress
if (actual < 1) {
downloadProgress.progress = actual + (recievedData/expectedTotalSize)
[NSTimer .scheduledTimerWithTimeInterval(0.05, invocation: self, repeats: false)]
}
}

Answer 1

You cannot update the progress because you do not have any progress. You've implemented the wrong way of downloading the data. Use the other way - the one where you get delegate messages. One of them tells you the progress. In particular, you'll implement
func URLSession(session: NSURLSession, dataTask: NSURLSessionDataTask, didReceiveData data: NSData {
Here you'll accumulate the data in an NSMutableData, and each time, you can compare the size of that accumulated data to the size of the expected total data, and thus you have the basis for updating the UIProgressView.