In the MasterViewController (created from the Master Detail template; or a new subclass of a UITableViewController), define an instance variable AppDelegate that is assigned in the viewDidLoad method:

class MasterViewController:UITableViewController {
  var app:AppDelegate!
  override func viewDidLoad() {
    app = UIApplication.sharedApplication().delegate
     as? AppDelegate
    …
  }
}

The table view controller provides data in a number of sections and rows. The numberOfSections method will return the number of users, with the section title being the username (indexed by the users list):

override func numberOfSectionsInTableView(tableView: UITableView)
 -> Int {
  return app.users.count
}
override func tableView(tableView: UITableView,
 titleForHeaderInSection section: Int) -> String? {
  return app.users[section]
}

The numberOfRowsInSection function is called to determine how many rows are present in each section. If the number is not known...