IOS Swift How can I get value from an Async method

Question

I am new to Swift and was wondering how can I get a value from an Async task. I have a function that gets Json data from an API on return I would like to get the value of a particular field outside of the async task... My code is below essentially I have a variable called status I want to get the value of status after the async called is returned then I want to check if the value is 1 . In the code below the value returned is 1 however it seems like the async called is executed before the line if Status == 1 {} . If the value is One then I want to navigate to a different ViewController . Any suggestions would be great ... I obviously can not put the code to go to a different ViewController inside the Async code since that is called many times .

 func GetData() {
   var status = 0
 // Code that simply contains URL and parameters
   URLSession.shared.dataTask(with:request, completionHandler: {(data, response, error) in
            if error != nil {
                print("Error")
            } else {
                do {

let parsedData = try JSONSerialization.jsonObject(with: data!, options: .allowFragments) as! [String:Any]

                    DispatchQueue.main.async {
                        if let Replies = parsedData["Result"] as? [AnyObject]  {


                            for Stream in Replies {

                                if let myvalue = Stream["status"] as? Int {
                                    status  = myvalue
                                }

                            }
                        }


                    }

                } catch let error as NSError {
                    print(error)
                }

            }

        }).resume()


       if status == 1 {
// This code is executed before the async so I don't get the value
        let nextViewController = self.storyboard?.instantiateViewController(withIdentifier: "Passed") as! Passed
        self.present(nextViewController, animated:false, completion:nil)
        }
}

You need to move last 4 lines to below for loop and it will work. — trungduc, May 04 '18 at 04:31
asynchronous task. Use a closure (https://stackoverflow.com/a/47713329/6822622) — AshvinGudaliya, May 04 '18 at 04:34

rv7284 · Accepted Answer · 2018-05-04T04:43:30.960

1

You can use a callback function for that like this:

func GetData(callback: (Int) -> Void) {
    //Inside async task, Once you get the values you want to send in callback
    callback(status)
}

You will get a callback from where you called the function.

For your situation, Anbu's answer will work too.

edited May 04 '18 at 04:43

answered May 04 '18 at 04:37

rv7284

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IOS Swift How can I get value from an Async method

1 Answers1