The Best Way to Connect Your iOS App to MySQL Database - parse data multiple times

Hi there everybody!
I am currently working on an app and I have used the tutorial “The Best Way to Connect Your iOS App to MySQL Database (4 Steps)” to connect the app to my database. In the tutorial Chris only parse data from his database once, but in my app I would like to parse data multiple times and update the tableview, for instance when I press a button. Do you know a way to do this? When I try to use the same methods as I do in the viewdidload-function I get an error code about something about an optional value is nil at the tableView.reloadData(). Are you able to help me with this?
Best regards
Christoffer