UITableView how to "dim" the actual table when UISearchbar gets focus?

Many of the table searches I see actually dim (change alpha?) of the actual tableView when the search bar gets focused. I am trying to implement this开发者_StackOverflow社区.

When I overload

- (void)searchBarTextDidBeginEditing:(UISearchBar *)searchBar

I am trying to do something like

self.tableView.alpha = .5f

But it is changing the alpha of the actual searchBar (if I have searchBar on its own) or changing the alpha of the entire table (including searchBar) if I have searchBar underneath the tableView in IB.

What am I doing wrong here. How can I just Dim the table and not everything.

I guess what I am really failing to understand is how all this stuff gets layered on the screen.

EDIT: The contacts application is a good example of what I am trying to do.

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Most such apps just throw a black-background UIView on top of the table and fade it in (to an alpha of .5 or whatever) when the search bar gains focus.

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If you use UISearchDisplayController, you get this behavior for free.

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Since iOS 8 (and up to at least iOS 9.2) you would use a UISearchController. Unfortunately, currently the interface builder supports only the now deprecated UISearchDisplayController. So, this is how to add it programmatically to your table view controller, including the dim effect:

let searchController = UISearchController(searchResultsController: nil)

override func viewDidLoad() {
    super.viewDidLoad()

    // Use the current view controller to update the search results:
    self.searchController.searchResultsUpdater = self
    self.searchController.dimsBackgroundDuringPresentation = true
    self.tableView.tableHeaderView = searchController.searchBar
}