has_many through children of self - ruby-on-rails

Question

I have some model, it is self-referential. It contains somethings, which can be child or parent, or both.
Is it possible to do something like this?
class Class < ActiveRecord::Base
belongs_to :parent, class_name: 'Class', foreign_key: :parent_id
has_many :children, class_name: 'Class', foreign_key: :parent_id
has_many :somethings, foreign_key: :something_id
has_many :somethings, through: :children, foreign_key: :something_id
end
What I want to do is call something like parent.somethings and get whole list of them.
For now all I get is stack level too deep error.
Without last line (has_many :somethings, through: :children, foreign_key: :something_id) I can only get child.somethings and it works perfectly.
So basically I want to get list of somethings, that includes somethings of every child of particular parent.
Thanks in advance!
P.S. I need exactly ActiveRecord::Associations::CollectionProxy, so creating method to collect somethings, I think is not possible.
P.P.S. Sorry, if my English is not so good :p

Answer 1

Actually I've found answer myself, after about an hour of research on Active Record Query Interface.
It's pretty simple, so I've done this:
class SomeClass < ActiveRecord::Base
belongs_to :parent, class_name: 'Class', foreign_key: :parent_id
has_many :children, class_name: 'Class', foreign_key: :parent_id
has_many :somethings
def all_somethings(order)
Something.joins(some_class: :parent).where("some_class_id = :id OR parents_some_classes.id = :id", {id: self.id}).uniq.order(order)
end
end
And I get exactly what I wanted!

Answer 2

I'd try splitting it into an instance method that gets all the children's somethings like this:
class Class < ActiveRecord::Base
belongs_to :parent, class_name: 'Class', foreign_key: :parent_id
has_many :children, class_name: 'Class', foreign_key: :parent_id
has_many :somethings, foreign_key: :something_id
def all_somethings
return unless self.children.empty?
(self.children + self.children.map(&:all_somethings)).uniq
end
end

Answer 3

I am writing an updated answer of Jonathan to avoid multiple call to :all_somethings and making query to get all the results. I hope this will also give you the results.
class Class < ActiveRecord::Base
belongs_to :parent, class_name: 'Class', foreign_key: :parent_id
has_many :children, class_name: 'Class', foreign_key: :parent_id
has_many :somethings, foreign_key: :something_id
has_many :childrens_somethings, through: :children, foreign_key: :something_id,
class_name: "Something"
def all_somethings
return unless self.children.empty?
(self.children + self.children_somethings).uniq
end
end