Json response with belongs_to

Hi all,

Supponsing I have this:

class Post < ActiveRecord::Base
end

class Comment < ActiveRecord::Base
  belongs_to :post
end

How can I make (on Rails 3) on the CommentsController to respond with
a json object including the related Post?

Thanks!

Anyone?

What I want is to inform Rails somehow that the json I want for the
comment should also contain information from the Post.