title: Cannot convert value of type '()' to expected argument type 'String'
body: <p>I am taking the zip code entered by my user and converting it into a City name. After it is converted to the City name I will save the information into my Firebase Database. I am getting an error "Cannot convert value of type '()' to expected argument type 'String'" when I try to do this. I am getting the zip code from a text field and passing it from the previous ViewController.
   <a href="https://i.stack.imgur.com/K4nGM.png" rel="nofollow noreferrer">error</a></p>
  
  <pre><code> //first ViewController
  
  
   override func prepare(for segue: UIStoryboardSegue, sender: Any?)
  {
  
  
      if let destination = segue.destination as? SignUpSecondViewController{
  
      destination.zipCode = zipCodeInput.text! 
      destination.name = nameText.text!
      destination.email = emailText.text!
      destination.password = passwordText.text!
      destination.pictureData = userImageView.image!
      }}
  
  }
  
     //second ViewController
  
      var zipCode = String()
  
   func getLocationFromPostalCode(postalCode : String){
      let geocoder = CLGeocoder()
  
      geocoder.geocodeAddressString(postalCode) {
          (placemarks, error) -&gt; Void in
          // Placemarks is an optional array of type CLPlacemarks, first item in array is best guess of Address
  
          if let placemark = placemarks?[0] {
  
              if placemark.postalCode == postalCode{
                  // you can get all the details of place here
                  print("\(placemark.locality)")
                  print("\(placemark.country)")
              }
              else{
                  print("Please enter valid zipcode")
              }
          }
      }
  }
  
  
  
  
   @IBAction func completeButtonAction(_ sender: Any) {
  
  let nameText = name
  let emailField = email.lowercased()
  let finalEmail = emailField.trimmingCharacters(in: .whitespacesAndNewlines)
  let location = getLocationFromPostalCode(postalCode: zipCode)
  let biography = bioTextView.text!
  let passwordText = password
  let interests = options.joined(separator: " , ")
  
      var pictureD: NSData?
  
  
      if let imageView = self.sentPic.image {
          pictureD = UIImageJPEGRepresentation(self.sentPic.image!, 0.70) as! NSData
      }
  
  
      if  finalEmail.isEmpty || biography.isEmpty || password.isEmpty || pictureD == nil {
          self.view.endEditing(true)
          let alertController = UIAlertController(title: "OOPS", message: " You must fill all the fields", preferredStyle: .alert)
          alertController.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: nil))
          present(alertController, animated: true, completion: nil)
  
      }else {
          SVProgressHUD.show()
  
          self.view.endEditing(true)
          authService.signUP(firstLastName: nameText, email: finalEmail, location: location, biography: biography, password: password, interests: interests, pictureData: pictureD as NSData!)
  
      }
      SVProgressHUD.dismiss()
  
  
      let storyboard = UIStoryboard(name: "Main", bundle: nil)
      let vc = storyboard.instantiateViewController(withIdentifier: "NewTabBarViewController") as! UIViewController
      // Alternative way to present the new view controller
       self.navigationController?.present(vc, animated: true, completion: nil)
  
  
  }
  </code></pre>