Can I narrow down the type of classes retrieved by a Polymorphic relationship in Rails?

I have a polymorphic relationship in Rails, but in one particular instance of use, I'd only like to retrieve records for a specific class.

What's the best approach to do this?

From stackoverflow Omega

• class Address < ActiveRecord::Base
    belongs_to :addressable, :polymorphic => true
  end
  
  class Person < ActiveRecord::Base
    has_many :addresses, :as => :addressable
  end
  
  class Company < ActiveRecord::Base
    has_many :addresses, :as => :addressable
  end
  
  >> c  = Company.create(:name => "WidgetCo")
  >> p  = Person.create(:name => "John Smith")
  >> a1 = Address.create(:street => "123 Foo ST", :city => "Barville", :state_code => "MT", :zip_code => "12345", :addressable => p)
  >> a2 = Address.create(:street => "321 Contact RD", :city => "Bazburg", :state_code => "MT", :zip_code => "54321", :addressable => c)
  >> Address.all(:conditions => { :addressable_type => Person.class_name })
  => [#<Address id: 1, street: "123 Foo ST" ... >]
  

  Omega : Mm, I should have clarified. This is a double-sided polymorphic relationship. I have: Users > Permission > Roles I'd like to get all roles a user belongs to, while stripping out any other records on the permission table. User.roles() Can I go: has_many :roles, :as => :resource, :through => :permission????

  Joel Meador : You might be able to use that has_many :through association, if your models are set up properly. Can you go into a little more detail about your models?
  From Joel Meador

• The rails plugin has_many_polymorphs can suit this purpose fairly well. You can define "getters" to pull specific data types out that are part of a polymorphic relationship.

  It is somewhat complicated and the documentation could afford to improve however.

  From Omega