问如何使用嵌套模型限制太阳黑子搜索？

EN

class SearchController < ApplicationController
  before_filter :fulltext_actions
  private
    def fulltext_actions
      @itineraries = do_fulltext_search(Itinerary)
      @users = do_fulltext_search(User)
      @itineraries_size = @itineraries.size
      @users_size = @users.size
    end
    def do_fulltext_search(model)
      Sunspot.search(model) do
        with(:is_available, true)
        fulltext params[:search]
      end.results
    end
end

class User < ActiveRecord::Base
  has_many :itineraries, :dependent => :destroy
  searchable do
    text :first_name, :boost => 3
    text :last_name, :boost => 3
    text :status
    boolean :is_available, :using => :available?
  end
  def available?
    !self.suspended
  end
end

class Itinerary < ActiveRecord::Base
  belongs_to :user
  searchable do
    text :title, :boost => 3
    text :budget
    text :description
    boolean :is_available, :using => :available?
  end
  def available?
    !self.user.suspended
  end
end