ios http post

import UIKit


class ViewController: UIViewController {
    @IBOutlet var passwordField: UITextField!
    @IBOutlet var usernameField: UITextField!

    @IBAction func LoginButton(_ sender: Any) {
        var request = URLRequest(url: URL(string: "http link here.")!)
        request.httpMethod = "POST"
        let postString = "username=\(usernameField.text!)&password=\(passwordField.text!)"
        request.httpBody = postString.data(using: .utf8)
        let task = URLSession.shared.dataTask(with: request) { data, response, error in
            guard let data = data, error == nil else {
                print("error=\(error)")
                return
            }

            let httpStatus = response as? HTTPURLResponse
            print("statusCode should be 200, but is \(httpStatus!.statusCode)")
            print("response = \(response)")
            print(postString)

            let responseString = String(data: data, encoding: .utf8)
            print("responseString = \(responseString)")

            if  (responseString?.contains("Incorrect"))!{
                DispatchQueue.main.async {
                    print("incorrect - try again")
                    let alert = UIAlertController(title: "Try Again", message: "Username or Password Incorrect", preferredStyle: UIAlertControllerStyle.alert)

                    alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler: nil))


                    self.present(alert, animated: true, completion: nil)
                }
            }

            else{
                DispatchQueue.main.async {
                    print("correct good")

                    let storyboard = UIStoryboard(name: "Main", bundle: nil)
                    let controller = storyboard.instantiateViewController(withIdentifier: "correctone")
                    self.present(controller, animated: true, completion: nil)
                }
            }
        }

        task.resume()
    }