问为什么在JQuery模型对话框中工作的observe_field代码不工作？

EN

        <%= label_tag :Search_by %>
         <select name="search" id="search" >
            <option value="0">Name</option>
            <option value="1">Trainer</option>
            <option value="2">Venue</option>
            <option value="3">Date</option>
         </select>

        <div id="div_to_be_updated" style="float:right">
            <%= render 'layouts/new_search' %>
        </div>

            <%= observe_field 'search', :update => 'div_to_be_updated',
            :url => {:controller => 'events', :action=> 'find' },
            :with => "'is_delivery_address=' + escape(value)" %>                 
        </div>

enter code here
def find
@trainers= Trainer.all
@countries= Country.all

        if ["0"].include?(params[:is_delivery_address])
            render :partial => 'layouts/new_search'
        else if ["2"].include?(params[:is_delivery_address])
            render :partial => 'layouts/venu_search'
        else if ["1"].include?(params[:is_delivery_address])
            render :partial => 'layouts/trainer_search'
        else
            # check element is date range...
            render :partial => 'layouts/date_search'

        end
        end
    end
end