I am having these objects:
class District < ActiveRecord::Base belongs_to :city end class City < ActiveRecord::Base has_many :districts end
Try this.. It will help....
index do column :city, :sortable => :"cities.name" do |district| district.city.human_name(:count => :other) if district.city.present? end end controller do def scoped_collection District.includes(:city) end end