Avoid multi-level associations using named scope

I had the a "local_address" method in Enrollment which looks for first local address

class Enrollment < ActiveRecord::Base

  has_many :addresses

  def local_address
    addresses.local.last
  end

end

class Address < ActiveRecord::Base
  
  belongs_to :enrollment
  belongs_to :address_type

  named_scope :local, { 
    :joins => "LEFT OUTER JOIN address_types ON address_types.id = addresses.address_type_id",
    :conditions => "address_types.name = 'Local'"
  }

end

Calling the "@enrollment.local_address" then leads to very unoptimized queries. To optimized it I had to call "Address.find" directly from the "local_address" method.

   def local_address
-    addresses.local.last
+    Address.last :include => :address_type, :conditions => ["address_types.name = 'Local' and enrollment_id = ?", id]
   end