activeAdmin, carrierwave, has_many files, reject_if attributes NOT present, allow_destroy

suits.rb

ActiveAdmin.register Suit do

  menu :parent => "Мебель",
       :label => "Комплекты"

  permit_params :title,
                :color,
                :material,
                :material_front,
                :price,
                :desc,
                :suit_photos_attributes => [:id,:image,:_destroy],
                :item_ids => [],
                :complect_ids => [],
                :special_prop_ids => []

  index do
    id_column
    column :title do |suit|
      "<div class='suit_title_in_table'>#{suit.title}</div>".html_safe
    end
    column :price
    column :items do |suit|
      lis = ((suit.items.map { |i|
          "<li>#{ image_tag i.image(:thumb) }</li>"
      }).join("")).html_safe
      "<ul class='suit_items_tn_table'>#{lis}</ul>".html_safe
    end
    column :special_props do |suit|
      admh_render_special_props_list(suit)
    end
    actions
  end

  form(:html => {:multipart => true}) do |f|
    f.inputs "Новый комплект" do
      f.input :title

      f.inputs "Фотографии комплекта" do
        f.has_many :suit_photos, :allow_destroy => true do |sph|
          # if sph.object.new_record?
            sph.input :image,
                      :as => :file,
                      :hint => sph.template.image_tag(sph.object.image)

          # else
          #   sph.template.image_tag(sph.object.image)
          # end
        end
      end

      f.input :complects,
              :as => :select,
              :input_html => {
                  :class => "suit_collection_selector",
                  :size => 1,
                  :multiple => false
              },
              collection: Complect.all

      f.input :color
      f.input :material
      f.input :material_front
      f.input :desc, :as => :ckeditor

      f.input :items,
              :as => :check_boxes,
              :label => "",
              :multiple => true,
              :collection => Item.where(:category_id => 2),
              :wrapper_html => {:class => 'suit_item_selector', :id => "sis_first"},
              :member_label => Proc.new { |it|
                "<img src='#{it.image(:thumb)}'/><br/>#{it.name}".html_safe
              }

      f.input :items,
              :label => "",
              :as => :check_boxes,
              :multiple => true,
              :collection => Item.where(:category_id => 1),
              :wrapper_html => {:class => 'suit_item_selector'},
              :member_label => Proc.new { |it|
                "<img src='#{it.image(:thumb)}'/><br/>#{it.name}".html_safe
              }

      f.input :items,
              :label => "",
              :as => :check_boxes,
              :multiple => true,
              :collection => Item.where(:category_id => 6),
              :wrapper_html => {:class => 'suit_item_selector'},
              :member_label => Proc.new { |it|
                "<img src='#{it.image(:thumb)}'/><br/>#{it.name}".html_safe
              }

      f.input :price
      f.input :special_props, :as => :check_boxes,
              :multiple => true,
              :member_label => Proc.new { |sp|
                "<img src='#{asset_path(sp.icon)}'/> #{sp.desc}".html_safe
              }

    end
    f.actions
  end

end

https://gist.github.com/c80609a/f31042c09bd56ba152ca