Correct polymorphic many-to-many associations

#Correct polymorphic many-to-many associations

#app/models/concerns

module Concerns
  module Moveable
    extend ActiveSupport::Concern

    included do
      has_many :moveable_locations, as: :moveable, dependent: :destroy
      has_many :locations, through: :moveable_locations
    end
  end
end

#app/models/train.rb

class Train < ActiveRecord::Base
  include Concerns::Moveable
end

#app/models/copter.rb

class Copter < ActiveRecord::Base
  include Concerns::Moveable
end

#app/models/truck.rb

class Truck < ActiveRecord::Base
  include Concerns::Moveable
end

#app/models/ship.rb

class Ship < ActiveRecord::Base
  include Concerns::Moveable
end

#db/migrations/create_moveable_locations.rb

class CreateMoveableLocations < ActiveRecord::Migration
  def change
    create_table :moveable_locations do |t|
      t.references :moveable, polymorphic: true
      t.references :location
      t.timestamps
    end
  end
end

#app/models/moveable_location.rb

class MoveableLocation < ActiveRecord::Base
  belongs_to :moveable, polymorphic: true
  belongs_to :location
end

#app/models/location.rb

class Location < ActiveRecord::Base
  has_many :moveable_locations, dependent: :destroy

  with_options :through => :moveable_locations, :source => :moveable do |location|
    has_many :trains, source_type: 'Train'
    has_many :copters, source_type: 'Copter'
    has_many :trucks, source_type: 'Truck'
    has_many :ships, source_type: 'Ship'
  end
end