composed_of with multiple Classes

Help! I'm trying to use composed_of to pull from multiple classes and can't figure out if it is possible or if there might be a better way to accomplish what i want.

I created standard_grade_strand_number, which references items in class Standard. HOWEVER, I don't want to see the the grade_id and strand_id in class Standard. I want to see the grade.name and strand.name in their respective classes.

Here's what I have (but not exactly what I want):

(model) class Standard < ActiveRecord::Base   belongs_to :grade   belongs_to :strand

  composed_of :standard_grade_strand_number,               :mapping => [ %w[grade_id grade_id],                             %w[strand_id strand_id],                             %w[number number] ]

(model) class StandardGradeStrandNumber < ActiveRecord::Base   attr_reader :grade_id, :strand_id, :number

  def initialize(grade_id, strand_id, number)     @grade_id = grade_id     @strand_id = strand_id     @number = number   end

  def to_s     [ @grade_id, @strand_id, @number ].compact.join("")   end end

Oh, here are the Strand and Grade models:

class Grade < ActiveRecord::Base   has_many :standards

class Strand < ActiveRecord::Base   has_many :standards

I've tried putting grade.name and strand.name in standard_grade_strand_number but can't make it work.

Do you have any ideas? Any thoughts? Do you see a better way to accomplish what I want? Thank you in advance!!!