如何在控制器中获取动态select_tag参数

Question

<%= @questions.each do |question| %>
   <%= select_tag "campaign_#{question['id']}",options_from_collection_for_select(current_advertiser.campaigns.all, "id", "title", selected_value || 0) %>
<% end %>

现在我如何在控制器中获取所选值。他们是动态的，然后我得到params[?]