Question

My application has about half a dozen different types of items that a user can comment on (articles, photos, videos, user profiles, blog posts, forum posts).

My plan right now is to have a single comments table in my database and then have parent_id and type fields in the table.

The type field would just be a string and the contents of it would be the name of it’s parent table. So for an Article comments, the type would be article, for example.

Is that the best way to handle the comments table? Or is there some other, more efficient way to do that?

Answer 1

Using a polymorphic association would be the best way to achieve this – check out Ryan’s railscast on the subject (or the ASCIIcast at http://asciicasts.com/episodes/154-polymorphic-association). I think you’ll end up with something like:

class Comment < ActiveRecord::Base

  belongs_to :commentable, :polymorphic => true
  belongs_to :user

end

Then each model you want users to be able to comment on will have the line:

has_many :comments, :as => :commentable

I also found this post useful when setting up polymorphic comments. Hope that helps!