Trying to Set Photo As A Mandatory Field during Signup with Pare

I am still new to coding. I have setup my signup screen but I wanted to make it mandatory to upload a profile picture during signup. I've tried to add and "if statement" to show an alert if the photo isn't uploaded but I haven't been successful getting it to work. Any suggestions? Here is my code:

class SignUpViewController: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate {

@IBOutlet var usernameField: UITextField!

@IBOutlet var activityIndicator: UIActivityIndicatorView!
@IBOutlet var message: UILabel!
@IBOutlet var emailField: UITextField!
@IBOutlet var passwordField: UITextField!
@IBOutlet var firstNameField: UITextField!
@IBOutlet var lastNameField: UITextField!

@IBOutlet var profilePic: UIImageView!




@IBAction func submitDataAction(sender: AnyObject) {


    var userName = usernameField.text
    var userEmail = emailField.text
    var userPassword = passwordField.text
    var firstName = firstNameField.text
    var lastName = lastNameField.text
    var initialImage = UIImage(named: "DidNotLoad")
    var picfile = profilePic.image
    let imageData = UIImagePNGRepresentation(picfile)
    let imageFile = PFFile(data: imageData)







    userEmail = userEmail.lowercaseString

    // Start activity indicator
    activityIndicator.hidden = false
    activityIndicator.startAnimating()

    var newUser = PFUser()
    newUser.username = userName.lowercaseString
    newUser.password = userPassword
    newUser.email = userEmail
    newUser["FirstName"] = firstName
    newUser["LastName"] = lastName
    newUser["ProfilePic"] = imageFile



    newUser.signUpInBackgroundWithBlock {(succeeded: Bool, error: NSError?) -> Void in
        if error == nil {
            dispatch_async(dispatch_get_main_queue()) {
                self.performSegueWithIdentifier("PushToEventsTableFromSignUp", sender: self)
            }

            self.activityIndicator.stopAnimating()
        }
        else {
            if let message: AnyObject = error!.userInfo!["error"] {
                self.message.text = "\(message)"

            }
        }
    }
}

@IBAction func uploadPhoto(sender: AnyObject) {
    //Create variable for image controller
    var picPhoto = UIImagePickerController()
    picPhoto.delegate = self
    picPhoto.sourceType = UIImagePickerControllerSourceType.PhotoLibrary
    picPhoto.allowsEditing = true
    self.presentViewController(picPhoto, animated: true, completion: nil)

}
func imagePickerController(picker: UIImagePickerController, didFinishPickingImage image: UIImage!, editingInfo: [NSObject : AnyObject]!) {

   self.dismissViewControllerAnimated(true, completion: { () -> Void in

    })

    profilePic.image = image
}


override func viewDidLoad() {
    super.viewDidLoad()
    self.makingRoundedImageProfileWithRoundedBorder()
    activityIndicator.hidden = true
    activityIndicator.hidesWhenStopped = true


    // Do any additional setup after loading the view.
}


private func makingRoundedImageProfileWithRoundedBorder() {
    self.profilePic.layer.cornerRadius = self.profilePic.bounds.size.width/2;
    self.profilePic.layer.masksToBounds = true
   // self.profilePic.clipsToBounds = true

    //Create Border around profile Pic
    self.profilePic.layer.borderWidth = 2.0
    self.profilePic.layer.borderColor = UIColor.whiteColor().CGColor
}