Question

First, I have a polymorphic association setup because comments can belong to any object(in my case post and articles).

I want to be able to say:

u = user.first
u.comments #This will list all comments from a user
u.comments.where(:commentable_type => "Post")  

This above line doesn’t work. it generates a sql:
SELECT “comments”.* FROM “comments” WHERE “comments”.”commentable_id” = 1 AND “comments”.”commentable_type” = ‘User’ AND “comments”.”commentable_type” = ‘Post’

obviously this would return an empty list because a comment can’t belong to 2 types. I also want to be able to say:

f = Food.first
f.comments.first.user #give me the user that posted the first comment

Here’s my basic model… any tips on changing this?

class Comment < ActiveRecord::Base
  belongs_to :commentable, :polymorphic => true
end

class Post < ActiveRecord::Base
  has_many :comments, :as => :commentable
end

class Article < ActiveRecord::Base
  has_many :comments, :as => :commentable
end

class User < ActiveRecord::Base
    has_many :comments, :as => :commentable
end

Answer 1

I think you should review your comment model, it should look like:

class Comment < ActiveRecord::Base
  belongs_to :user
  belongs_to :commentable, :polymorphic => true
end

So you’d have two relationships, the first will point to who posted the comment, the other will point to the object being commented.

Comment.first.user # this will return the user

Comment.first.commentable # this will return the object which the comment was attached (Post, Article or ?Food?)

Dont forget the migrations if you wish to try this approach.