I wanted to allow a user to type in the address for their community and then instantly inform them whether the address they wanted was available.

In my controller:

        def check_portal_url
        end

In my view:

<%@comm = Portal.find_by_portal_url(@params[:search])   %>
<%if @comm%>
                <%=@params[:search]%> is taken, please try a different address.
<%else%>
                <%=@params[:search]%> is available.
<%end%>

and in my form

 

<%= observe_field(:portal_portal_url,
                 :frequency => 0.5,
                 :update => :observe_results,
                 :loading => "Element.show('spinner')",
                 :complete => "Element.hide('spinner')",
                 :url => { :controller=>'ajax',:action => 'check_portal_url'  },
                :with => "'search=' + escape(value)"
                ) %>


 

<div id="observe_results"></div>
In the above, the

                :with => "'search=' + escape(value)"

part is very important as without it, the value of the field will be very hard to access.