Question

我尝试使用其父级的update_attributes创建一个新的嵌入式对象。在mongoid 2.0.0.beta20中，这个工作正常，但在更新到2.3.3后，这失败了。

要重现，您可以使用此模型结构：

class Bird
  include Mongoid::Document
  embeds_one :egg
  accepts_nested_attributes_for :egg
end

class Egg
  include Mongoid::Document
  field :weight, :type => Integer, :default => 10
  field :size, :type => Array, :default => [10,10]

  def height=(value)
    self.size[0] = value
  end

  def width=(value)
    self.size[1] = value
  end

  def height
    self.size[0]
  end

  def width
    self.size[1]
  end

end

然后，在ruby控制台中运行：

b = Bird.new
 => #<Bird _id: 4eb163660d996a3e43000002, _type: nil>
b.update_attributes "egg" => { "height" => 20, "weight" => 20 }
NoMethodError: You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.[]=
from (irb):14:in `height='
from vendor/ruby/1.9.1/gems/mongoid-2.3.3/lib/mongoid/attributes/processing.rb:98:in `process_attribute'
from vendor/ruby/1.9.1/gems/mongoid-2.3.3/lib/mongoid/attributes/processing.rb:26:in `block in process'
from vendor/ruby/1.9.1/gems/mongoid-2.3.3/lib/mongoid/attributes/processing.rb:24:in `each_pair'
from vendor/ruby/1.9.1/gems/mongoid-2.3.3/lib/mongoid/attributes/processing.rb:24:in `process'
from vendor/ruby/1.9.1/gems/mongoid-2.3.3/lib/mongoid/document.rb:131:in `block in initialize'
from vendor/ruby/1.9.1/gems/mongoid-2.3.3/lib/mongoid/threaded/lifecycle.rb:84:in `_building'
from vendor/ruby/1.9.1/gems/mongoid-2.3.3/lib/mongoid/document.rb:127:in `initialize'
from vendor/ruby/1.9.1/gems/mongoid-2.3.3/lib/mongoid/factory.rb:23:in `new'
from vendor/ruby/1.9.1/gems/mongoid-2.3.3/lib/mongoid/factory.rb:23:in `build'
from vendor/ruby/1.9.1/gems/mongoid-2.3.3/lib/mongoid/relations/builders/nested_attributes/one.rb:30:in `build'
from vendor/ruby/1.9.1/gems/mongoid-2.3.3/lib/mongoid/attributes/processing.rb:137:in `block in process_relations'
from vendor/ruby/1.9.1/gems/mongoid-2.3.3/lib/mongoid/attributes/processing.rb:134:in `each_pair'
from vendor/ruby/1.9.1/gems/mongoid-2.3.3/lib/mongoid/attributes/processing.rb:134:in `process_relations'
from vendor/ruby/1.9.1/gems/mongoid-2.3.3/lib/mongoid/attributes/processing.rb:122:in `process_pending'
from vendor/ruby/1.9.1/gems/mongoid-2.3.3/lib/mongoid/attributes/processing.rb:29:in `process'
from vendor/ruby/1.9.1/gems/mongoid-2.3.3/lib/mongoid/attributes.rb:133:in `block in assign_attributes'
from vendor/ruby/1.9.1/gems/mongoid-2.3.3/lib/mongoid/threaded/lifecycle.rb:26:in `_assigning'
from vendor/ruby/1.9.1/gems/mongoid-2.3.3/lib/mongoid/attributes.rb:132:in `assign_attributes'
from vendor/ruby/1.9.1/gems/mongoid-2.3.3/lib/mongoid/attributes.rb:154:in `write_attributes'
from vendor/ruby/1.9.1/gems/mongoid-2.3.3/lib/mongoid/persistence.rb:115:in `update_attributes'
from (irb):36
from vendor/ruby/1.9.1/gems/railties-3.1.1/lib/rails/commands/console.rb:45:in `start'
from vendor/ruby/1.9.1/gems/railties-3.1.1/lib/rails/commands/console.rb:8:in `start'
from vendor/ruby/1.9.1/gems/railties-3.1.1/lib/rails/commands.rb:40:in `<top (required)>'
from script/rails:6:in `require'
from script/rails:6:in `<main>'system :037 >

这是因为嵌入对象在设置新值之前未初始化。这就是为什么size数组没有初始化，因此仍然是零。使用mongoid-2.0.0.beta20（我升级），一切正常。有什么我想念的吗？新的mongo-2.3.3是否期望ME首先初始化嵌入对象！？

感谢您提供任何帮助。

Answer 1

默认值现在在设置了所有其他属性后应用，以防您使用proc作为有条件依赖其他属性的默认值。你的身高=和宽度=方法现在需要注意这一点。

请参阅：

https://github.com/mongoid/mongoid/issues/1075

mongoid.update_attributes在新的嵌入对象上失败

1 个答案: