viewing response from URLSession - swift3

Question

I have an endpoint which takes in a phone number and sends a code to the number, but also returns that same message to the data section of the session that called it.
All of that works, but the problem I'm having is that, after the session makes the call, I'm segueing to the next screen and i'm passing that code into the next controller. But i think the api is responding too slow, so by time the segue (and prep for segue) has happened the code has not been returned yet. How can i fix this?
let scriptURL = "https://---------------/api/verify/sms?"
let urlWithParams = scriptURL + "number=\(phone.text!)"
let myUrl = NSURL(string: urlWithParams)
let request = NSMutableURLRequest(url: myUrl! as URL)
request.httpMethod = "GET"
let task = URLSession.shared.dataTask(with: request as URLRequest) {
data, response, error in
//print(error?.localizedDescription)
do {
let json = try JSONSerialization.jsonObject(with: data!, options: .allowFragments) as AnyObject
self.currentCode = json["code"]!! as! String //-> This is the code the is returned from the api call
}catch{
print("error with serializing JSON: \(error)")
}
}
task.resume()
self.performSegue(withIdentifier: "toVerifyCode", sender: (Any?).self)
}
// MARK: - Navigation
// In a storyboard-based application, you will often want to do a little preparation before navigation
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
// Get the new view controller using segue.destinationViewController.
// Pass the selected object to the new view controller.
if segue.identifier == "toVerifyCode"{
let newController = segue.destination as! verifyCodeController
newController.code = self.currentCode
}
}

Answer 1

The problem is that you placed self.performSegue(withIdentifier: "toVerifyCode", sender: (Any?).self) not in the closure.
So, you have to place it like this:
let task = URLSession.shared.dataTask(with: request as URLRequest) {
data, response, error in
//print(error?.localizedDescription)
do {
let json = try JSONSerialization.jsonObject(with: data!, options: .allowFragments) as AnyObject
//on main thread
DispatchQueue.main.async {
self.currentCode = json["code"]!! as! String //-> This is the code the is returned from the api call
self.performSegue(withIdentifier: "toVerifyCode", sender: (Any?).self)
}
}catch{
print("error with serializing JSON: \(error)")
}
}
task.resume()
Also, please note that your closure is executed asynchronously, so I wrapped the call to be executed on main thread by using GCD.