Question

In my Rails application, I have two models, Articles and Projects, which are both associated with a user. I want to add comments to each of these models. What’s the best way to structure this?

Here’s my current setup:

class Comment < ActiveRecord::Base
  belongs_to :article
  belongs_to :project
end

class Article < ActiveRecord::Base
  belongs_to :user
  has_many :comments
end

class Project < ActiveRecord::Base
  belongs_to :user
  has_many :comments
end

class User < ActiveRecord::Base
  has_many :articles
  has_many :projects
  has_many :comments, :through => :articles
  has_many :comments, :through => :projects
end 

Is this the right way to handle the structure? If so, how do I manage the CommentsController to have an article_id if it was created through an Article, and a project_id if it was created through a Project? Are there special routes I should set up?

One final comment: Comments don’t always have to have a user. Since this if for my website, I want anonymous viewers to be able to leave comments. Is this a trivial task to handle?

Answer 1

Make Comment a polymorphic model. Then create a polymorphic association.

Here’s an example of polymorphic relationship from the Rails wiki and here’s a Railscast from the screencast-men Ryan Bates.