class Admin::ItemsController < ApplicationController

  def index
    item_resource = ItemResource.new(params)
    @items = item_resource.fetch_for_index
    @form = item_resource.form
  end
end

class Admin::ItemResource
  include AdminBits

  def filters
    [:having_name, :price_between]
  end

  def having_name(filter_params)
    resource_class.having_name(filter_params[:name])
  end

  def price_between(filter_params)
    # ...
  end

  def ordering
    [:name, :price]
  end

  def default_order
    :price
  end

  def default_direction
    :desc
  end
end