AWS Dynamo DB Object Mapper Error

I am trying to query my AWS Dynamo DB table "UserCreds" via swift code. I have first defined a class and then mapped it to Dynamo DB table. Then I am calling AWSDynamoDBQueryExpression() to search for a row on this table. but the program keeps crashing with following error:

"ViewController11viewDidLoadFS0_FT_T_L_11DDBTableRow dynamoDBTableName]: unrecognized selector sent to class 0x102ec3d40]"

I have also ensured that I have correct credentials setup in the AppDelegate file. Any insight into the reasons why this could be failing would be much appreciated. Thanks!

Below is what the code looks like:

import UIKit

class ViewController: UIViewController {

override func viewDidLoad() {
    super.viewDidLoad()


    class DDBTableRow :AWSDynamoDBObjectModel {

        var UserIdentifier:String?
        var UserFullName:String?


        class func dynamoDBTableName() -> String! {
            return "UserCreds"
        }

        class func hashKeyAttribute() -> String! {
            return "UserIdentifier"
        }

        class func rangeKeyAttribute() -> String! {
            return "UserFullName"
        }

        //MARK: NSObjectProtocol hack
        override func isEqual(object: AnyObject?) -> Bool {
            return super.isEqual(object)
        }

        override func `self`() -> Self {
            return self
        }
    }


    //SEARCH FOR A ROW
    let dynamoDBObjectMapper = AWSDynamoDBObjectMapper.defaultDynamoDBObjectMapper()

    let queryExpression = AWSDynamoDBQueryExpression()
    queryExpression.indexName = "UserIdentifier-UserFullName-index"
    queryExpression.hashKeyAttribute = "UserIdentifier"
    queryExpression.hashKeyValues = "1234"
    queryExpression.scanIndexForward = true

    dynamoDBObjectMapper.query(DDBTableRow.self, expression: queryExpression).continueWithExecutor(AWSExecutor.mainThreadExecutor(), withBlock: { (task:AWSTask!) -> AnyObject! in
        if (task.error != nil) {
            print("Error: \(task.error)")

            let alertController = UIAlertController(title: "Failed to query a test table.", message: task.error.description, preferredStyle: UIAlertControllerStyle.Alert)
            let okAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.Cancel, handler: { (action:UIAlertAction) -> Void in
            })
            alertController.addAction(okAction)
            self.presentViewController(alertController, animated: true, completion: nil)
        } else {
            if (task.result != nil) {
                print(task.result)
            }
            print("Performing Segue")
        }
        return nil
    })

}