ruby on rails - how do i get the id of the selected item in dropdown -

<%= form_for(:offer,:url=>{:controller=>'offers',:action=>'combo'}) |f|%>

<%= f.select :catid_get, options_from_collection_for_select(@categories, "id", "name"), prompt: "select category" %>

i new in rails.i have dropdown categories there.when select category dropdown want category id in controller,so can use id it's child dropdown.

select

each select option in html has 2 values -- value , label:

<select>   <option value="volvo">volvo</option>   <option value="saab">saab</option>   <option value="mercedes">mercedes</option>   <option value="audi">audi</option> </select> 

it's value passed controller. means if able create select tag in rails app correct value / label setup, pass correct data require.

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rails

here's how i'd handle it:

<%= form_for :offer, offers_combo_path |f|%>    <%= f.collection_select :cat_id, @categories, :id, :name, prompt: "select category" %> 

this pass following params categories_controller:

#app/controllers/categories_controller.rb class categoriescontroller < applicationcontroller    def combo       params[:offer][:cat_id]    end end 

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recommendation

i'd recommend use form_tag helper this, rather form_for. reason being form_for activerecord objects, , although can use :symbols in helper, need use less elaborate system

i'd replace form_for following:

<%= form_tag offer_combo_path %>   <%= collection_select :cat_id, @categories, :id, :name, prompt: "select category" %> <% end %>