ViewControllerWithTableView.swift

   override func scrollViewDidScroll(scrollView: UIScrollView) {
        // when reaching bottom, load a new page
        if scrollView.contentOffset.y == scrollView.contentSize.height - scrollView.bounds.size.height
        {
            // fetch next page of results
            //self.footerActivityIndicator.startAnimating()
            self.dataPaginator.fetchNextBatch()
        }
    }
    
    private final class Paginator {
    
    var offset:Int = 0
    
    var challengeId : String!
    
    var responseHandler:([Image] throws -> ())!
    
    func fetchNextBatch() {
        
        Store.instance.getImages(fromChallenge: challengeId,offset: String(offset)).onComplete { (result) in
            switch result {
                
                case .Success(let images):
                    
                    if !images.isEmpty {
                        self.offset += 10
                        _ = try? self.responseHandler(images)
                        self.fetchNextBatch()
                    }
                
            default:
                break
            }
        }
    }
}