use cocoon to create nested

controller.rb

  accepts_nested_attributes_for :tour_irregular_schedules,
                                allow_destroy: true, reject_if: proc { |a| a["start_date"].blank? && a['all_season_flg'].blank? }

views

<div class="control-group">
  <%= f.label 'イレギュラースケジュール', class:'control-label' %>
  <div class="controls" id="tour_irregular_schedule_controls">
    <%= f.fields_for :tour_irregular_schedules do |tour_irregular_schedule_fields| %>
      <%= render "tour_irregular_schedule_fields", f: tour_irregular_schedule_fields %>
    <% end %>
    <p><%= link_to_add_association "イレギュラースケジュール追加", f, :tour_irregular_schedules %></p>
  </div>
</div>