facenovel/app/models/comment.rb

class Comment < ApplicationRecord
  validates :author_id, :post_id, :body, presence: true

  belongs_to :author,
    foreign_key: :author_id,
    class_name: :User
  
  belongs_to :post,
    foreign_key: :post_id,
    class_name: :Post
  
  belongs_to :parent_comment,
    foreign_key: :parent_id,
    class_name: :Comment,
    optional: true
  
  has_many :child_comments,
    foreign_key: :parent_id,
    class_name: :Comment
end