How to implement a search bar above the keyboard like Safari on iPad

How can I insert a UISearchBar in the middle of the shortcuts bar displayed above the keyboard on iPad?
You insert custom shortcuts in the shortcuts bar using 'someTextField.inputAssistantItem' with 'leadingBarButtonGroups' or 'trailingBarButtonGroups' properties, but it has no 'middleBarButtonGroups'.
If I add the search bar as 'inputAccessoryView', like 'someTextField.inputAccessoryView = UISearchBar()' it is added above the shortcuts bar.