ruby-on-rails - 通过关联获取 has_many 的 ActiveRecord::RecordInvalid 错误；连接表上的验证问题

Question

我有如下三个关联模型:

class Product < ActiveRecord::Base
  belongs_to :user
  has_many :descriptions, {
    dependent: :destroy,
    before_add: [:add_user_id_to_description, :validate_description]
  }
  has_many :documents, through: :descriptions

  # ...

  def validate_description(d)
    unless d.valid?
      d.errors[:user_id].each do |err|
        self.errors.add(:base, "Doc error: #{err}")
      end
    end
  end
end

class Document < ActiveRecord::Base
  belongs_to :user
  has_many :descriptions, {
    dependent: :destroy,
    before_add: [:add_user_id_to_description, :validate_description]
  }
  has_many :products, through: :descriptions
end

class Description < ActiveRecord::Base
  belongs_to :user
  belongs_to :product
  belongs_to :document
end

当我做类似的事情时:

doc = user.documents.build
doc.update_attributes(:product_ids => [1,2])

并且 description 验证失败，然后我得到 false 和 doc 上的相应错误。这正是我想要的。

但是，如果 doc 已经存在，例如:

doc = user.documents.first
doc.update_attributes(:product_ids => [1,2])

并且 description 验证失败，然后我得到一个 ActiveRecord::RecordInvalid 错误。

我很清楚为什么会这样——insert_record 方法来自 has_many_through_association.rb在内部调用 save!，它会传播错误。它提前退出，跳过此调用，以获取新记录。

有什么方法可以设置我的模型来防止这种保存!？还是我被迫从错误中拯救？

编辑

我已经尝试了下面 Carlos Drew 描述的设置；我还尝试设置 validates_associated :descriptions，并将 inverse_of::whatever 添加到 has_many :descriptions 选项哈希。我还尝试在 Product 和 Document 模型上设置一个 before_validation 回调，但显然关联回调首先运行(？)。每次尝试似乎都会产生完全相同的错误消息。

我正在从下面的控制台粘贴我的错误跟踪。

Document Load (1.8ms)  SELECT "documents".* FROM "documents" WHERE "documents"."user_id" = 19 ORDER BY "documents"."id" DESC LIMIT 1
   (1.0ms)  BEGIN
  Product Load (41.7ms)  SELECT "products".* FROM "products" WHERE "products"."id" = $1 LIMIT 1  [["id", 3640]]
  Product Load (4.1ms)  SELECT "products".* FROM "products" INNER JOIN "descriptions" ON "products"."id" = "descriptions"."product_id" WHERE "descriptions"."document_id" = 3552
  User Load (7.0ms)  SELECT "users".* FROM "users" WHERE "users"."id" = 19 LIMIT 1
  Account Load (2.0ms)  SELECT "accounts".* FROM "accounts" WHERE "accounts"."user_id" = 19 LIMIT 1
   (0.9ms)  SELECT COUNT(*) FROM "descriptions" WHERE "descriptions"."user_id" = 19
   (1.2ms)  ROLLBACK
ActiveRecord::RecordInvalid: Validation failed: User You have reached limit of 1
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/validations.rb:56:in `save!'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/attribute_methods/dirty.rb:33:in `save!'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/transactions.rb:264:in `block in save!'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/transactions.rb:313:in `block in with_transaction_returning_status'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/connection_adapters/abstract/database_statements.rb:192:in `transaction'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/transactions.rb:208:in `transaction'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/transactions.rb:311:in `with_transaction_returning_status'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/transactions.rb:264:in `save!'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/associations/has_many_through_association.rb:85:in `save_through_record'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/associations/has_many_through_association.rb:52:in `insert_record'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/associations/collection_association.rb:496:in `block (2 levels) in concat_records'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/associations/collection_association.rb:344:in `add_to_target'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/associations/collection_association.rb:495:in `block in concat_records'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/associations/collection_association.rb:493:in `each'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/associations/collection_association.rb:493:in `concat_records'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/associations/collection_association.rb:134:in `block in concat'
... 14 levels...
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/associations/builder/collection_association.rb:71:in `block in define_writers'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/attribute_assignment.rb:85:in `block in assign_attributes'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/attribute_assignment.rb:78:in `each'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/attribute_assignment.rb:78:in `assign_attributes'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/persistence.rb:216:in `block in update_attributes'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/transactions.rb:313:in `block in with_transaction_returning_status'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/connection_adapters/abstract/database_statements.rb:192:in `transaction'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/transactions.rb:208:in `transaction'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/transactions.rb:311:in `with_transaction_returning_status'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.13/lib/active_record/persistence.rb:215:in `update_attributes'
    from (irb):2
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/railties-3.2.13/lib/rails/commands/console.rb:47:in `start'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/railties-3.2.13/lib/rails/commands/console.rb:8:in `start'
    from /usr/local/rvm/gems/ruby-1.9.3-p125/gems/railties-3.2.13/lib/rails/commands.rb:41:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>'

Answer 1

我的直觉是您过度设计了带有 before_add::validate_description 的模型验证。您没有使用标准的 Rails/ActiveRecord 方法和约定吗？具体来说，validates: true可以设置关联模型之间的验证处理。

关于关联验证仍然存在一些陷阱，我建议阅读以下内容:

• has_many association validations on new vs. existing records
• validates_associated
• Thoughtbot article on :inverse_of wrt to association validations (我认为这不一定与您的设置相关)

编辑

我对此非常好奇，并按照您的描述通过规范(在 public github project 中)复制了该问题。我仍然认为手动 before_add 验证设计过度，我没有使用它们，但我遇到了您描述的问题。

所以，我想了解的是，您遇到的情况是否符合预期和期望。如果不自以为是，Rails 就什么都不是，也许使用 has_many-through 关联的直接设置是一种编码人员注意用例。明确地说，您正在做的事情有点奇怪:当您要求设置 document.product_ids 时，您实际上正在做的是在某些描述对象上设置匹配的 document_id 和 product_id。正确的？这很奇怪，而且意图/预期结果非常不清楚。

那么有什么替代方法呢？您正在做的是向文档添​​加描述，而这些描述是关于产品的。那么，为什么不通过描述界面与文档产品进行交互呢？我认为，这应该避免 has_many-through setter 怪异，并提供更清晰的界面。