Question

I have this polymorphic association where a user can have many comments, a school can have many comments, and a comment can have many comments (or in my naming case replies):

class Comment < ActiveRecord::Base
  attr_accessible :content
  has_many :replies, :as => :commentable, :class_name => "Comment" # replies to comments

  belongs_to :commentable, :polymorphic => true
  belongs_to :commentor, :class_name => "User", :foreign_key => "user_id"
end

class User < ActiveRecord::Base
  has_many :comments, :as => :commentable
  has_many :commentors, # all users who commented on a user
    :through => :comments,
    :source => :commentor
end

class School < ActiveRecord::Base
  has_many :comments, :as => :commentable
  has_many :commentors, # all users who commented on a school
    :through => :comments,
    :source => :commentor
end

In the User, I can retrieve all who commented on a user using @user.commentors. Same goes for School, i.e. @school.commentors.

For the comments model, I would like to acheive the same thing for the Comments model where I can find all the commentors (or I guess repliers) to a comment; however, I have no idea what kind of association to create since a has_many :through association will not work like how it worked for the User and School model.

Answer 1

Use this:

has_many :reply_commentors, :through => :replies, :source => :commentor