Named scopes that re-use other named scopes via proxy_options

gistfile1.rb

class Parent < ActiveRecord::Base
  named_scope :ready, :conditions => { :ready_at => true }
  has_many :children
end

class Child < ActiveRecord::Base
  belongs_to :parent

  named_scope :ready, lambda {
    :joins => :parent,
    :conditions => Parent.ready.proxy_options[:conditions] }
end