Having 2 foreign keys from one table in the same table rails

Question

I am trying to implement comment replying feature to my project, however i am not very sure with the method i m using. My basic idea is to keep all the comments in one table, while having another table comments_replies which will have the parent comment(comment) and the comment(reply). now i have something like this is migrations of comments_replies:

create_table :comments_replies do |t|
  t.integer :parent_comment_id, index: true, foreign_key_column_for: :comments, null: false
  t.integer :reply_comment_id, index: true, foreign_key_column_for: :comments, null: false
  t.timestamps null: false
end

and in model comments_reply.rb

belongs_to :comment, class_name: 'Comment'

and in model comment.rb

has_many :comments_replies, foreign_key: :parent_comment_id, foreign_key: :reply_comment_id

as for the second part since i m trying to use RSPEC for testing purposes, in model comments_reply_spec.rb i have:

require 'rails_helper'

RSpec.describe CommentsReply, type: :model do
  let(:comments_reply) { create(:comments_reply) }
  subject { comments_reply }

  it { is_expected.to respond_to(:parent_comment_id) }
  it { is_expected.to respond_to(:reply_comment_id) }
end

but i am not sure how to test this case properly, so any suggestions would be appreciated

Answer 1

What you are trying to achieve could be done from "Comment" model itself. You just need another column 'parent_id' in "Comment" which will reference to parent Comment in same table. For all those main "Comments"(which are not replied to any comment) column 'parent_id' will be null.

So your model will look like below

class Comment 
  belongs_to :parent_comment, foreign_key: :parent_comment_id, class_name: 'Comment'
  has_many :replies, foreign_key: :parent_comment_id, class_name: 'Comment'
end

With your current approach

You have specify association with two foreign_key which is wrong. In your "Comment" model you need to association. 1) for all replies of a comment 2) For getting parent comment.

has_many :comments_replies, foreign_key: :parent_comment_id
has_many :replies, through: :comment_replies

has_one :parent_comment_reply, foreign_key: :reply_comment_id, class_name: 'CommentReply'
has_one :parent_comment, through: :parent_comment_reply

Also in your CommentReply model

belongs_to :parent_comment, foreign_key: :parent_comment_id, class_name: 'Comment'
belongs_to :reply_comment, foreign_key: :reply_comment_id, class_name: 'Comment'

Your specs looks like below

require 'rails_helper'

RSpec.describe CommentsReply, type: :model do
  let(:parent_comment){ create(:comment) }
  let(:child_comment) { create(:comment) }

  let(:comment_reply) { create(:comment_reply, parent_comment_id: parent_comment.id, reply_comment_id: child_comment.id) }

  subject { comment_reply }

  it { is_expected.to respond_to(:parent_comment_id) }
  it { is_expected.to respond_to(:reply_comment_id) }

  it "should correctly identify the parent/child relationship" do
    expect(comment_reply.reply_comment.id).to be_eql(child_comment.id)
    expect(comment_reply.parent_comment.id).to be_eql(parent_comment.id)
  end

end