IOS Swift - go to another view after getting stats from NURLSESSION - ios

Question

Once the user click the login button, i will call the func LoginClicked and get the status from api:
func LoginClicked(sender: AnyObject)
{
data_request{
(response) -> () in
let arrResponse = response.componentsSeparatedByString("|")
if (arrResponse[2] == "1"){
self.performSegueWithIdentifier("Login", sender: self)
}
else {
let alert = UIAlertController(title: "Login Failed", message: "Invalid Login!", preferredStyle: UIAlertControllerStyle.Alert)
alert.addAction(UIAlertAction(title: "Click", style: UIAlertActionStyle.Default, handler: nil))
self.presentViewController(alert, animated: true, completion: nil)
}
}
}
func data_request(completion : (response:NSString) -> ()){
let txtUI : String = txtUsername!.text!
let txtPWD : String = txtPassword!.text!
let url = NSURL(string: "http://myweb.net/?UI=\(txtUI)&PW=\(txtPWD)")!
let request = NSURLRequest(URL: url)
let config = NSURLSessionConfiguration.defaultSessionConfiguration()
let session = NSURLSession(configuration: config)
let task = session.dataTaskWithRequest(request, completionHandler: {
(
let data, let response, let error) in
guard let _:NSData = data, let _:NSURLResponse = response where error == nil else {
print("error")
return
}
let dataString = NSString(data: data!, encoding: NSUTF8StringEncoding)
completion(response : dataString!)
})
task.resume()
}
If success, it will move to another view. Otherwise, show failed alert. it will hit the error BAD_EXECUTION_INSTRUCTION when calling self. in both condition.

Answer 1

After get the hint from #Tj3n, it can do the proper action now.
func data_request(completion : (response:NSString) -> ()){
let txtUI : String = txtUsername!.text!
let txtPWD : String = txtPassword!.text!
let url = NSURL(string: "http://myweb.net/?UI=\(txtUI)&PW=\(txtPWD)")!
let request = NSURLRequest(URL: url)
let config = NSURLSessionConfiguration.defaultSessionConfiguration()
let session = NSURLSession(configuration: config)
let task = session.dataTaskWithRequest(request, completionHandler: {
(
let data, let response, let error) in
guard let _:NSData = data, let _:NSURLResponse = response where error == nil else {
print("error")
return
}
dispatch_async(dispatch_get_main_queue(), {
let dataString = NSString(data: data!, encoding: NSUTF8StringEncoding)
//let response = dataString?.componentsSeparatedByString("|")
//print(dataString)
//print(response![2])
let arrResponse = dataString!.componentsSeparatedByString("|")
if (arrResponse[2] == "1"){
self.performSegueWithIdentifier("Login", sender: self)
}
else {
let alert = UIAlertController(title: "Login Failed", message: "Invalid Login!", preferredStyle: UIAlertControllerStyle.Alert)
alert.addAction(UIAlertAction(title: "Click", style: UIAlertActionStyle.Default, handler: nil))
self.presentViewController(alert, animated: true, completion: nil)
}
})
let dataString = NSString(data: data!, encoding: NSUTF8StringEncoding)
completion(response : dataString!)
})
task.resume()
}