Abstract BaseClass, Polymorphism [,MixIns]

[Atastor]

Oooookay...this might be a bit over the top, but it might hint at another problem more relevant.

In general you use Mixins to share common functionality in Ruby/Ruby on Rails. In several of my recent projects I choose abstract superclasses, instead; at the same time I used polymorphism. I.e.

class Parent < ActiveRecord::Base

  self.abstract_class = true

  has_one :xxx, :as => :poly_xxx

  has_many :documents, :through => :xxx, :readonly => false

  [more shared document handling stuff]

end

class Xxx < ActiveRecord::Base

  belongs_to :special_xxx, :polymorphic => true

  [...]

end

class Document < ActiveRecord::Base

  belongs_to :xxx

  [...]

end

class ChildA < Parent

  [special stuff A]

end

class ChildB < Parent

  [special stuff B]

end

So far there had been no problems nesting the documents into ClassA and ClassB etc.:

class ChildBsController < ApplicationController

  active_scaffold :child_b do |conf|

    [...]

    conf.nested.add_link(:documents)

  end

  [...]

end

Everything worked like a charm, I could freely list, created and update the attached documents via the nested action link. 

All of a sudden it stopped working; alas, because this was in a non-tested part (*BLUSH*), I can't pin it down to any specific recent update. Doing some debugging, though, I was able to localize it somewhere in the vicinity of the abstract base_class, because the parameter hash contained a hash key parent_id, where it so far contained the hash key child_b_id.

As I was not able to locate the trouble spot. I switched to using a Mixin instead of the abstract base_class, and everything is working fine again.

Nevertheless, this seems to hint at an AS problem with finding the reverse association under the described –not so common– circumstances.

Regards

Michael

[Atastor]

Sorry, :poly_xxx and :special_xxx were meant to be the same.