polymorphic migration

gistfile1.rb

rails g migration Something attachable:polymorphic
or
rails g scaffold Something attachable:polymorphic

may can generate migration like this:

  def self.up
    create_table :somethings do |t|
      t.references attachable, polymorphic => true

and model

class Something < ActiveRecord::Base
  belongs_to :attachable, :polymorphic => true