class Admin::BaseFilrator
  def filtered_by?()
  end

  def get_filter()
  end
end

class Admin::CompaniesFiltrator < Admin::BaseFiltrator
  pattr_initialize :params

  def filtered_by_
end

class ...

  def joins_for_collection
    result = []
    %w(region test_packet statistics).each { |filter| send("filter_by_#{filter}", result) }
    result.join(' ')
  end

  def filter_by_region
    if bla-lba-bla
      ...
    end
  end
end