Auto complete onclick

I’d like to know how I can put the id in a field when the user clicks on an autocomplete item. I have a field with autocomplete where I wanna show the name of the user but save on the database the id. My code is the following one:
<%= text_field_with_auto_complete :user_id, :name, {:size => 15}, {:url => users_path, :method => :get, :param_name => ‘search’} %>
Thanks in advance

Rodrigo,

You can either use a hidden field for the ID or follow the approach
covered by Ryan Bates in the following railscast:

http://railscasts.com/episodes/102-auto-complete-association

Cheers, Sazima