heightForRowAtIndexPath not called

[kilolumen]

    // Set the CustomNavigationBar as delegate for a UIScrollView 
    func setupPulltoRefresh(scrollView:UIScrollView){
        if let navbar = self.customNavigationBar(){
            scrollView.delegate = navbar
        }
    }

the method not called

    override func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
        return 300
    }