extract rendering condition

app/models/champs/drop_down_list_champ.rb

@@ -1,3 +1,7 @@
 class Champs::DropDownListChamp < Champ
   THRESHOLD_NB_OPTIONS_AS_RADIO = 5
+
+  def render_as_radios?
+    drop_down_list.enabled_non_empty_options.size <= THRESHOLD_NB_OPTIONS_AS_RADIO
+  end
 end

app/models/champs/multiple_drop_down_list_champ.rb

@@ -23,6 +23,10 @@ class Champs::MultipleDropDownListChamp < Champ
     value.present? ? selected_options.join(', ') : nil
   end
 
+  def render_as_checkboxes?
+    drop_down_list.enabled_non_empty_options.size <= THRESHOLD_NB_OPTIONS_AS_CHECKBOX
+  end
+
   private
 
   def format_before_save