text_from_textfield_of_alert_controller.swift

func performLogin(alertController: UIAlertController) {
        guard let textFields = alertController.textFields else { return  }
        var params = [String:String]()
        for textField in  textFields{
            if textField.placeholder == "Enter username"{
                params["username"] = textField.text
            }
            if textField.placeholder == "Enter password"{
                params["password"] = textField.text
            }
        }
        print("login params \(params)")
    }