JSON seems to execute after all other code - ios

Question

The following Swift code has to run twice in order to display the JSON data in a label. On the first run the label simply remains blank. It seems to me that the issue could be something along the lines of the JSON part of the code runs last, but I can't figure out why. I have included the code below. I'm still a rookie, so be gentle :D
class ViewController: UIViewController {
#IBOutlet weak var labelDegrees: UILabel!
#IBOutlet weak var labelSpeed: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
// Set logo in nav bar
navigationItem.titleView = UIImageView(image: UIImage(named: "logo"))
// Global save values
var appDel: AppDelegate = UIApplication.sharedApplication().delegate as AppDelegate
var context: NSManagedObjectContext = appDel.managedObjectContext!
// JSON Fetching
let urlPath = "http://api.openweathermap.org/data/2.5/weather?lat=55.564120&lon=12.568605"
let url = NSURL(string: urlPath)
let session = NSURLSession.sharedSession()
let task = session.dataTaskWithURL(url!, completionHandler: {data, response, error -> Void in
if (error != nil) {
println(error)
}
else {
// Delete old entries in CoreData
var request = NSFetchRequest(entityName: "WindData")
request.returnsObjectsAsFaults = false
var results = context.executeFetchRequest(request, error: nil)
for result in results! {
context.deleteObject(result as NSManagedObject)
context.save(nil)
}
// Start fetching JSON
let jsonResult = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: nil) as NSDictionary
var item = jsonResult["wind"] as NSDictionary
var degrees:Float = item["deg"] as Float
var speed:Float = item["speed"] as Float
// Start saving JSON
var newItem = NSEntityDescription.insertNewObjectForEntityForName("WindData", inManagedObjectContext: context) as NSManagedObject
var speedValue:Float = speed as Float
var degreesValue:Float = degrees as Float
newItem.setValue(speedValue, forKey: "speed")
newItem.setValue(degreesValue, forKey: "degrees")
context.save(nil)
}
})
task.resume()
// Start fetching from CoreData
var request = NSFetchRequest(entityName: "WindData")
request.returnsObjectsAsFaults = false
var results = context.executeFetchRequest(request, error: nil)
if results!.count > 0 {
for result in results as [NSManagedObject] {
let degrees:Float = result.valueForKey("degrees")! as Float
let speed:Float = result.valueForKey("speed")! as Float
if speed > 6.0 {
self.labelDegrees.text = "Go kitesurf: \(speed) m/s"
}
else {
self.labelDegrees.text = "Stay in: \(speed) m/s"
}
}
}
else {
println("No data")
}
}

Answer 1

You are actually fetching the data on another thread with dataTaskWithURL.So you need to write // Start fetching from CoreData code in dataTaskWithURL.As dataTaskWithURL will not immediately executed so // Start fetching from CoreData code will get called first while dataTaskWithURL is fetching the data.So replece the code with below
class ViewController: UIViewController {
#IBOutlet weak var labelDegrees: UILabel!
#IBOutlet weak var labelSpeed: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
// Set logo in nav bar
navigationItem.titleView = UIImageView(image: UIImage(named: "logo"))
// Global save values
var appDel: AppDelegate = UIApplication.sharedApplication().delegate as AppDelegate
var context: NSManagedObjectContext = appDel.managedObjectContext!
// JSON Fetching
let urlPath = "http://api.openweathermap.org/data/2.5/weather?lat=55.564120&lon=12.568605"
let url = NSURL(string: urlPath)
let session = NSURLSession.sharedSession()
let task = session.dataTaskWithURL(url!, completionHandler: {data, response, error -> Void in
dispatch_async(dispatch_get_main_queue(),{
if (error != nil) {
println(error)
}
else {
// Delete old entries in CoreData
var request = NSFetchRequest(entityName: "WindData")
request.returnsObjectsAsFaults = false
var results = context.executeFetchRequest(request, error: nil)
for result in results! {
context.deleteObject(result as NSManagedObject)
context.save(nil)
}
// Start fetching JSON
let jsonResult = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: nil) as NSDictionary
var item = jsonResult["wind"] as NSDictionary
var degrees:Float = item["deg"] as Float
var speed:Float = item["speed"] as Float
// Start saving JSON
var newItem = NSEntityDescription.insertNewObjectForEntityForName("WindData", inManagedObjectContext: context) as NSManagedObject
var speedValue:Float = speed as Float
var degreesValue:Float = degrees as Float
newItem.setValue(speedValue, forKey: "speed")
newItem.setValue(degreesValue, forKey: "degrees")
context.save(nil)
}
// Start fetching from CoreData
var request = NSFetchRequest(entityName: "WindData")
request.returnsObjectsAsFaults = false
var results = context.executeFetchRequest(request, error: nil)
if results!.count > 0 {
for result in results as [NSManagedObject] {
let degrees:Float = result.valueForKey("degrees")! as Float
let speed:Float = result.valueForKey("speed")! as Float
if speed > 6.0 {
self.labelDegrees.text = "Go kitesurf: \(speed) m/s"
}
else {
self.labelDegrees.text = "Stay in: \(speed) m/s"
}
}
}
else {
println("No data")
}
});
})
task.resume()
}