Json and variable scope - ios

Question

My error should be quite obvious but I can't find it;
I've a global variable initialized a the beginning of my class:
class InscriptionStageViewController: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource {
var lesSemaines = [String]()
I try to populate this array with a distant json file using that function
func getSemainesStages(){
let url = URL(string: "http://www.boisdelacambre.be/ios/json/semaines.json")
let task = URLSession.shared.dataTask(with: url!){ (data, response, error) in
if let content = data {
do {
let myJson = try JSONSerialization.jsonObject(with: content, options: JSONSerialization.ReadingOptions.mutableContainers) as AnyObject
let listeSemaines = myJson["semaine"] as! [[String:AnyObject]]
//print(listeSemaines)
for i in 0...listeSemaines.count-1 {
var tabSem = listeSemaines[i]
let intituleSemaine:String = tabSem["intitule"] as! String
//let dateSemaine:String = tabSem["date"] as! String
DispatchQueue.main.sync
{
self.lesSemaines.append(intituleSemaine)
}
}
} catch
{
print("erreur Json")
}
}
}
task.resume()
}
When I call my function in the viewDidLoad and then I print my global array, it's empty (the URL is correct, the json data is read correctly and when I read the data appended in the array in the loop, it print the (so) needed value...)
Thanks in advance

Answer 1

The download takes time. Introduce another methode:
func updateUi() {
print(lesSemaines)
//pickerView.reloadAllComponents()
}
And call it after the download finished:
func getSemainesStages(){
// ... your code
let task = URLSession.shared.dataTask(with: url!){ (data, response, error) in
// ... your code
for tabSem in listeSemaines{
guard let intituleSemaine = tabSem["intitule"] as? String else {
print("erreur Json")
continue
}
self.lesSemaines.append(intituleSemaine)
}
// update UI *after* for loop
DispatchQueue.main.async {
updateUi()
}
// ... your code
}
}

Answer 2

I have updated your code to Swift 3. Please replace it with below code.
func getSemainesStages(){
let url = URL(string: "http://www.boisdelacambre.be/ios/json/semaines.json")
let task = URLSession.shared.dataTask(with: url!){ (data, response, error) in
if let content = data {
do {
let myJson = try JSONSerialization.jsonObject(with: content, options: JSONSerialization.ReadingOptions.mutableContainers) as! [String: Any]
let listeSemaines = myJson["semaine"] as! [[String: Any]]
for i in 0...listeSemaines.count-1 {
var tabSem = listeSemaines[i]
let intituleSemaine:String = tabSem["intitule"] as! String
self.lesSemaines.append(intituleSemaine)
}
print(self.lesSemaines)
} catch {
print("erreur Json")
}
}
}
task.resume()
}