comment_threads.rb

# I was working on a client project not long back and the client expressed an interest in having thread-able comments, where someone can reply to one comment and it starts off a new thread of comments, which could then be branched even further by other replies. It occurred to me that I already had a polymorphic association with my comments so that different resources could be commented on (articles, photos, statuses, etc...). It seemed plausible I could just go ahead and use this on a self-referential basis as well. 
# With polymorphic associations, instead of having a foreign key like, article_id, you have a type column representing the table and an id column for whatever type table that is. For instance:
:commendable_type => 'Article', :commendable_id => 1
# Would be comparable to a foreign key reference of 
:article_id => 1
#thus polymorphic models can be associated with any other model type, including themselves it turns out.  
:commendable_type => 'Comment' 
# Represents a comment that belongs to a comment. 
class Comment < ActiveRecord::Base
  belongs_to :commentable, polymorphic: true
  has_many :comments, as: :commentable
  belongs_to :user
end
# So one way to have comment threads is simply to comment on a comment. This worked well. Go ahead and try it.
# it's another take on self-referential associations but without using alias classes.