UISearchBar in navigationbar

To put searchBar into the center of navigationBar:

self.navigationItem.titleView = self.searchBarTop;

To put searchBar to the left/right side of navigationBar:

UIBarButtonItem *searchBarItem = [[UIBarButtonItem alloc] initWithCustomView:searchBar];
self.navigationItem.rightBarButtonItem = searchBarItem;

As of iOS 7, the UISearchDisplayController supports this by default. Set the UISearchDisplayController's displaysSearchBarInNavigationBar = YES to get this working easily.

Per the documentation:

Starting in iOS 7.0, you can use a search display controller with a navigation bar (an instance of the UINavigationBar class) by configuring the search display controller’s displaysSearchBarInNavigationBar and navigationItem properties.

As one commenter noted, using searchDisplayController.displaysSearchBarInNavigationBar = true ends up hiding any existing left/right bar button items.

I've found two different ways of adding a searchBar to a navigationBar using iOS7's new property on searchDisplayController.

1) Nib Based Approach

If you're using a .xib, you can set a User Defined Runtime Attribute for this value and for whatever reason, the leftBarButtonItem stays in tact. I have not tested it with a rightBarButtonItem.

2) Code (Timing Matters)

If you want to implement in code, timing seems to matter. It seems that you must add the searchBar to the navigationBar first, then set your barButtonItem.

- (void)viewDidLoad
{
    ...
    self.searchDisplayController.displaysSearchBarInNavigationBar = true;
    self.navigationItem.leftBarButtonItem = [UIBarButtonItem new];
    ...
}

Check out Apple's UICatalog sample code. It shows how to use the new UISearchController in three different ways: modally, in nav bar, and below the navigation bar.

Objective C code snippet for UISearchBar in NavigationBar

- (void)viewDidLoad {
    UISearchController *searchController = [[UISearchController alloc] initWithSearchResultsController:nil];
    
    if (@available(iOS 11.0, *)) {
        self.navigationItem.searchController = searchController;
    } else {
        self.navigationItem.titleView = searchController.searchBar;
    }
}

Read more here