Modeling polymorphic has_many :through

gistfile1.txt

A user creates Spaces (rooms), Items (things), and Profiles (people).
Reservations are used to schedule times when these three models are in use and cannot be used elsewhere.
Since the modeling of a thing that can only be in use in one place/activity is common to Spaces, Items, and Profiles, this common functionality makes up the polymorphic model Resource.

Reservation
  belongs_to :manager, :class_name => "Profile"
  
  has_many :reservation_lines, :before_add => :set_nest, :dependent => :destroy
  has_many :profiles, :through => :reservation_lines, :source => :reservable, :source_type => 'Profile'
  has_many :spaces, :through => :reservation_lines, :source => :reservable, :source_type => 'Space'
  has_many :items, :through => :reservation_lines, :source => :reservable, :source_type => 'Item'

  accepts_nested_attributes_for :reservation_lines, :allow_destroy => true,
      :reject_if => proc {|attributes| attributes['reservable_id'].blank?}

ReservationLine
  belongs_to :reservation
  belongs_to :reservable, :polymorphic => true

Profile
  include ReservableMixin

Space
  include ReservableMixin

Item
  include ReservableMixin



module ReservableMixin
  def self.included(base)
    base.has_many :reservation_lines, :as => :reservable
    base.has_many :reservations, :through => :reservation_lines
  end

  def reservations_overlapping(range)
    overlapping = reservations.select {|r| r.range.overlap?(range)}
  end
end

I assume you have five tables:

reservations, reservation_lines, profiles, spaces, and item. And only the reservation_lines table has (two) foreign keys: reservation_id and reservable_id (with reservable_type). is that right?

Yep. The only foreign keys (ignoring the one for manager of a reservation) are reservation_id (:integer) and reservable_id (:integer) and reservable_type (:string).

Awesome. Thanks. I've been trying to map something like this for a while now and have been making do with ugly hackery. Cheers!

…

On Tue, Apr 26, 2011 at 9:30 PM, superlou < ***@***.***>wrote: Yep. The only foreign keys (ignoring the one for manager of a reservation) are reservation_id (:integer) and reservable_id (:integer) and reservable_type (:string). ## Reply to this email directly or view it on GitHub: https://gist.github.com/935790

I'm new to this, so take this with a grain of salt. Good luck railsing!