Fritz Anderson wrote: > SUMMARY: How do I assign objects, of different subclasses of an abstract > class, to a belongs_to relation? > > I had the following class hierarchy: > > Location < ActiveRecord::Base > Address < Location > Building < Location > > and a class Person with these relationships: > has_one :address, :dependent => :destroy > belongs_to :building > > Location is backed by table "locations," and Person by "People." > > I had to refactor to insert an abstract class between Location and > Building: > > Location < ActiveRecord::Base > Address < Location > SharedLocation < Location > Building < SharedLocation > DeletedLocation < SharedLocation > > I now want Person#building to refer to either a Building or a > DeletedLocation. Refactoring the foreign key and accessor would be a > major pain. > > I changed the relation for Person#building to: > belongs_to :building, :class_name => 'SharedLocation', > :foreign_key => 'building_id' > > (:foreign_key because I got a deprecation warning on specifying > :class_name without one.) > > I also moved > has_many :people, :dependent => :nullify > from Building to SharedLocation. In the course of flailing about for a > solution, I added ":foreign_key => 'building_id'", but I don't know what > I'm doing. > > I ran my unit tests for setting the relation, and am now seeing > failures/errors, all of which seem to boil down to this: Attempting > person = Building.new(...) > gets an AssociationTypeMismatch, "SharedLocation expected, got > Building." > > How do I make belongs_to relations polymorphic? > > Rails 2.3.2 > ruby 1.8.7 (2008-08-11 patchlevel 72) [universal-darwin10.0]
First off, I disagree with your use of polymorphism in this problem domain. You could keep location a top level class along with a status field which could simply hold the values 'building', or 'deleted'. Choose sub classing for changes and/or additions to functionality vs changes and/or additions to state. Anyways, disregarding the above.. take a look at this excellent podcast by Bates that explains it as well as any.. http://railscasts.com/episodes/154-polymorphic-association hth ilan -- Posted via http://www.ruby-forum.com/. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
