- if params[:item] # we are dealing with a form with validation errors so fill in the last known value for sub_category
  = f.select :sub_category_id, options_for_select(@options_for_sub_category, params[:item][:sub_category_id]), {}, :class => 'required'
- elsif params[:uuid] # an edit action
...

def format_category_list(sub_categories)
    count = sub_categories.count
    list = ""
...

@merged << @array1
@merged << @array2
@merged.flatten!
...