如何使用 Mongoid 更新 Rails 中嵌套的 Mongo 文档属性？

（如果这个问题缺乏细节，请提前道歉，我会看评论并添加我能添加的内容）

我有一个具有以下内容的模型：

class Product
  include Mongoid::Document
  include Mongoid::Timestamps
#...
  field :document_template, :type => Document
  accepts_nested_attributes_for :document_template

在文档 document_template 中，是以下引用_many，我要修改它。具体来说，我想更改引用的字体：

class Document
  include Mongoid::Document
  include Mongoid::Timestamps
#...
  references_many :fonts, :stored_as => :array, :inverse_of => :documents

我的控制器和表单中应该有什么样的逻辑和细节才能完成这项工作？如果您希望我添加一些我尝试过的滑稽的事情，请发表评论；然而，我对其中任何一个都没有任何运气。

这是使用 Rails 控制台快速显示问题的方法：

# Grab a Product and check how many fonts are in it's document_template
ruby-1.8.7-p302 > prod = Product.find(:first)
 => ...
ruby-1.8.7-p302 > prod._id
 => BSON::ObjectId('4d06af15afb3182bf5000111') 
ruby-1.8.7-p302 > prod.document_template.font_ids.count
 => 9

# Remove a font from the font_ids array
ruby-1.8.7-p302 > prod.document_template.font_ids.pop
 => BSON::ObjectId('...')    # This font id was removed from font_ids
ruby-1.8.7-p302 > prod.document_template.font_ids.count
 => 8

# Save the changes
ruby-1.8.7-p302 > prod.document_template.save!
 => true 
ruby-1.8.7-p302 > prod.save!
 => true 

# Instantiate a new product object of that same product
ruby-1.8.7-p302 > prod_new = Product.find(:first)
 => ...

# Confirm the _ids are the same
ruby-1.8.7-p302 > prod._id == prod_new._id
 => true 

# Check to see if the changes were persisted
ruby-1.8.7-p302 > prod_new.document_template.font_ids.count
 => 9  # If the changes persisted, this should be 8.

# Grrrrr... doesn't look like it. Will the change disappear after a reload too?

ruby-1.8.7-p302 > prod.reload
 => ...
ruby-1.8.7-p302 > prod.document_template.font_ids.count
 => 9

# ಠ_ಠ ... no dice.

使用 mongo（而不是 Rails 中的 mongoid）更新对象可以按预期工作。

凯尔·班克 (Kyle Banker) 要求提供一些日志信息，所以就在这里。不幸的是，我找不到比 Rails 服务器的输出更好的日志记录源，这似乎表明从未进行更新调用。对于某些上下文，这里是来自控制器的一些信息：

def update_resource(object, attributes)
  update_pricing_scheme(object, attributes)
  update_document_template_fonts(object, attributes)
end

def update_document_template_fonts(object, attributes)
  document_template = object.document_template
  document_template_attributes = attributes[:document_template_attributes]

  font_ids = document_template_attributes[:font_ids]
  font_ids.delete("") # Removing an empty string that tags along with the font_ids.
  font_ids.collect! { |f| BSON::ObjectId(f) } # Mongo want BSON::ObjectId

  object.document_template.font_ids.replace font_ids
  object.document_template.save!(:validate => false)
  object.save!(:validate => false)
end

以下是处理 POST 时 Rails 服务器的输出：

Started GET "/admin/products/4d091b18afb3180f3d000111" for 127.0.0.1 at Wed Dec 15 13:57:28 -0600 2010

Started POST "/admin/products/4d091b18afb3180f3d000111" for 127.0.0.1 at Wed Dec 15 13:57:49 -0600 2010
  Processing by Admin::ProductsController#update as HTML
  Parameters: {"commit"=>"Update Product", "authenticity_token"=>"QUW0GZw7nz83joj8ncPTtcuqHpHRtp1liq8fB7/rB5s=", "utf8"=>"✓", "id"=>"4d091b18afb3180f3d000111", "product"=>{"name"=>"Ho Ho Ho Flat Multiple Photo Modern Holiday Card", "document_template_attributes"=>{"id"=>"4d091b18afb3180f3d000112", "font_ids"=>["", "4d091b17afb3180f3d000023"]}, "description"=>"", "pricing_scheme_id"=>"4d091b17afb3180f3d00003b"}}

development['users'].find({:_id=>BSON::ObjectId('4d091b17afb3180f3d00009b')}, {}).limit(-1)
development['products'].find({:_id=>BSON::ObjectId('4d091b18afb3180f3d000111')}, {}).limit(-1)
development['pricing_schemes'].find({:_id=>BSON::ObjectId('4d091b17afb3180f3d00003b')}, {}).limit(-1)

MONGODB development['products'].update({"_id"=>BSON::ObjectId('4d091b18afb3180f3d000111')}, {"$set"=>{"updated_at"=>Wed Dec 15 19:57:50 UTC 2010}})

in Document#set_default_color_scheme: self.color_scheme = #<ColorScheme:0xb52f6f38>

MONGODB development['documents'].update({"_id"=>BSON::ObjectId('4d091b18afb3180f3d000112')}, {"$set"=>{"color_scheme_name"=>"green_charcoal_black", "updated_at"=>Wed Dec 15 19:57:50 UTC 2010}})

Redirected to http://localhost:3000/admin/products/4d091b18afb3180f3d000111
Completed 302 Found in 49ms

看起来更新 font_ids 的 MONGODB 命令完全不存在......

我偏偏相信导致了问题。上面的日志记录表明产品的 document_template.fonts （或 font_ids）已更新，这似乎与错误描述相符。

（旁注：如果不是 :stored_as => :array，我有点困惑 font_ids 数组到底来自哪里。我不是 100% 确定我应该修改哪个but因为 font_ids 是一个数组，而 fonts 是一个 Mongoid::Criteria，所以阻力最小的路径是 font_ids。）

从数据的角度来看，:field 和 :embeds_* 似乎很相似，因为信息都嵌入到父文档中。