The apple way to do this is to show an activity indicator on top of the table view.
You can check the Native Mail app to work.

-
UIRefreshControl *refreshControl = [[UIRefreshControl alloc] init];
[refreshControl addTarget:self action:@selector(handleRefresh:) forControlEvents:UIControlEventValueChanged];
self.refreshControl = refreshControl;
/ .
- beginRefreshing
- endRefreshing