This is what Im trying to do whenever a DetailCategory is selected it updates the _details_subs partial

_detail_subs.haml

- @detail_subs.each do |sub|                                                                                  
  .form-group                                                                                               
    = sub.title                                                                                              
    = f.select(:detail_category_ids, options_from_collection_for_select(sub.details, 'id', 'title'), {}, class: 'chosen-select-detail form-control')                                                                          
                      

_form.haml

= f.select(:detail_category_ids, options_from_collection_for_select(@detail_category, 'id', 'title'), {}, class: 'chosen-select-detail form-control')
.form-grup
  #detail_subs
  
:javascript
$(".chosen-select-detail").chosen().change(
  function() {
  #when detail_category is changed i want it to load the detail_subs for the detail_category
  }
 );
  

entries_controller.rb

def new                                                                                                    
  @entry = Entry.new                                                                                      
  @detail_category = DetailCategory.all                                                                    
  @detail_subs = @detail_category.first.detail_subs      
end