[ACCEPTED]-Understanding Rails ActiveRecord "single model" self joins-activerecord

Accepted answer
Score: 27

I was missing the has_many foreign key to 6 "parent_post_id". Once its set, the post.replies 5 will reference other Post instances by parent_post_id.

The 4 posts.rb model has the relationship defined:

class Post < ActiveRecord::Base
  has_many :replies, :class_name => "Post",
    :foreign_key => "parent_post_id"
  belongs_to :parent_post, :class_name => "Post",
    :foreign_key => "parent_post_id"

I 3 can now create Posts, assign a parent_post_id 2 to a different Post, then later get all 1 Posts that are replies to any parent Post.

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