ruby-on-rails-3 - 以引用对象为标准的 mongoid 范围

Question

我对 Rails 3 中的 Mongoid 模型有以下范围:

class Expert
  include Mongoid::Document
  referenced_in :category

   scope :currently_available, lambda { |category, limit|
    limit ||= 5
    {
      :where => {:category => category, :state => 'available'}, 
      :limit => limit
    }
  }

category这是引用模型的一个实例:

class Category
  include Mongoid::Document
  references_many :experts, :inverse_of => :category

当我将范围称为 Expert.currently_available(Category.first, 5) 时，我得到了一个 Criteria 对象:

ruby-1.9.2-p136 :110 > Expert.currently_available(Category.first, 5)
 => #<Mongoid::Criteria
  selector: {:category=>#<Category _id: 4d95ea8773fdea4c47000003, _type: nil, _id: BSON::ObjectId('4d95ea8773fdea4c47000003'), title: "Tax Advisors", price: 5.5>, :state=>"available"},
  options:  {:limit=>5},
  class:    Expert,
  embedded: false>

问题是:如何在此条件下加载集合？当我这样做时 .to_a ， 它说: Cannot serialize an object of class Category into BSON
当直接拾取时，类别本身是有效的 BSON obj，但在范围内它无法呈现引用 obj。

提前致谢!

Answer 1

这对我有用(Mongoid 2.0):

:where => {:category_id => category.id, :state => 'available'}