ActiveAdmin: sort by child association's property

Question

I am having these objects:

class District < ActiveRecord::Base
  belongs_to :city
end
class City < ActiveRecord::Base
  has_many :districts
end
         


        

Answer 1

Very simple and readable solution:

index do
  column :city, sortable: "cities.name"
end

controller do
  def scoped_collection
    # join cities
    super.includes :city
  end
end