Rails 3.2.3:如何批量分配关联模型?

我有一个 rails 3.2.3，我有一个带有两个嵌套模型的表单，当我尝试提交表单时，出现此错误:

I have a rails 3.2.3, I have a form with two nested models, when I try to submit the form, I get this error:

ActiveModel::MassAssignmentSecurity::Error in ExperimentsController#create

Can't mass-assign protected attributes: descriptions_attributes, circuits_attributes

这是我的模型:

class Experiment < ActiveRecord::Base
  attr_accessible :title, :intro_text

  has_many :circuits, :dependent => :destroy
  has_many :descriptions, :dependent => :destroy


  accepts_nested_attributes_for :descriptions, :reject_if => lambda { |a| a[:data].blank? }, :allow_destroy => true
  accepts_nested_attributes_for :circuits, :reject_if => lambda { |a| a[:data].blank? }, :allow_destroy => true

end

class Circuit < ActiveRecord::Base
  attr_accessible :data, :title

  belongs_to :experiment
end

class Description < ActiveRecord::Base
  attr_accessible :data, :title

  belongs_to :experiment
end

我可以为字段添加 attr_accessible，但是，嵌套模型呢?

I can add attr_accessible for a field, but, what about the nested models ?