how to pass a nil value for one of the parameter in alamofire Post request
<p>I would like to pass a nil value i.e., optional to one of the parameter value. And it must proceed with the nil value in the <strong>Alamofire Post request</strong> .It would be helpful if you tell me how to proceed next?</p>

<pre><code>    let image: UIImage = UIImage()
    let imageData = UIImagePNGRepresentation(image)
    let base64String = imageData?.base64EncodedStringWithOptions(.Encoding64CharacterLineLength)

    let parameters = [
        "first_name": "XXXXX",
        "email" : "1234@gmail.com",
        "password" : "password",
        "profile_picture" : base64String]

Alamofire.request(.POST, "http://abc/public/user/register", parameters: parameters, encoding: .JSON, headers: nil)

        .progress { bytesWritten, totalBytesWritten, totalBytesExpectedToWrite in
            print(totalBytesWritten)

            // This closure is NOT called on the main queue for performance
            // reasons. To update your ui, dispatch to the main queue.
            dispatch_async(dispatch_get_main_queue()) {
                print("Total bytes written on main queue: \(totalBytesWritten)")
           }
        }
        .responseJSON { response in
            debugPrint(response)
    }
</code></pre>

<p>The response should gets succeeded even if the <strong>profile_pictures</strong> is empty. I know it can be done with optional chaining but don't know how to proceed!!</p>