console

ree-1.8.7-2011.03 :020 > c
 => #<Comment id: 3, body: "foo!", commentable_id: 111, commentable_type: "Post", user_id: 18, created_at: "2011-07-13 15:25:49", updated_at: "2011-07-27 18:19:04", helpful_at: "2011-07-27 18:19:04", research_report_id: nil> 

ree-1.8.7-2011.03 :021 > c.commentable.class
 => Post(id: integer, title: string, method_of_exchange: string, you_tube_url: string, lat: decimal, lng: decimal, bounty: integer, distance: integer, user_id: integer, consider_similar_offers: boolean, description: text, created_at: datetime, updated_at: datetime, address: string, city: string, state: string, zip: string, country: string, county: string, category_id: integer, slug: string, status: string, popularity: integer, delta: boolean, share_count: integer, needs_comment: decimal, needs_offer: decimal, district: string, concierge_flag: string, request_details: text) 

ree-1.8.7-2011.03 :023 > c.commentable.blah
NoMethodError: undefined method `blah' for "#<Post:0x1058e57f0>":Post
	from /Users/patrick/.rvm/gems/ree-1.8.7-2011.03@foo/gems/activerecord-3.0.7/lib/active_record/associations/association_proxy.rb:216:in `method_missing'
	from (irb):23

ree-1.8.7-2011.03 :024 > c.commentable.id
 => 111 

ree-1.8.7-2011.03 :025 > p = Post.find(111)
 => #<Post id: 111, title: "foobar", created_at: "2011-07-02 20:59:05", updated_at: "2011-11-09 21:00:19"
> 
ree-1.8.7-2011.03 :026 > p.blah
 => "blah!"

post and comment

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

      def method_missing(name, *args, &block)
        puts "blah!"
      end
    end

    class Comment < ActiveRecord::Base

      belongs_to :commentable, :polymorphic => true

    end