test

class Comment < ActiveRecord::Base
  validates :author_id, :post_id, :content, presence: true

  belongs_to :author,
    class_name: "User",
    foreign_key: :author_id

  belongs_to :post

  #where primary key = value of foreign key
  belongs_to :parent,
    class_name: "Comment",
    foreign_key: :parent_comment_id

  #where their foreign key is equal to the value of the primary key (id)
  has_many :child_comments,
    class_name: "Comment",
    foreign_key: :parent_comment_id

end