我有三个相关的模型：
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])
description验证失败，然后我false获得了doc和doc上的相应错误。这正是我想要的。
但是，如果doc = user.documents.first
doc.update_attributes(:product_ids => [1,2])
已经存在，例如：
description ActiveRecord::RecordInvalid验证失败，然后我收到insert_record错误。
我确切知道为什么会发生这种情况 - 来自has_many_through_association.rb的save!方法在内部调用save!，这会传播错误。它会提前退出，跳过此调用，以获取新记录。
我是否可以通过某种方式设置模型来阻止此rescue？或者我从错误中被迫validates_associated :descriptions？
修改
我已经尝试了下面Carlos Drew描述的设置;我还尝试设置inverse_of: :whatever，并将has_many :descriptions添加到before_validation选项哈希中。我还尝试在Product和Document模型上设置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>'
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。
{{1}}
答案 0 :(得分：2)
我的直觉是你用before_add: :validate_description过度设计了模型的验证。你没有标准的Rails / ActiveRecord方法和约定吗？具体而言，可以为关联模型之间的验证处理设置validates: true。
尽管如此，关联验证仍有一些问题，我建议您阅读以下内容：
修改
我对此感到非常好奇，然后通过规格（并且它在public github project中）来复制问题，正如您所描述的那样。我仍然认为手册before_add验证是过度设计的，我没有使用它们，但我遇到了你描述的问题。
所以，我想要了解的是你所遇到的是否是预期和期望的。如果没有自以为是的话，Rails就没有任何意义，并且可能使用has_many-through关联的直接设置是一种编码器提防的用例。要清楚，你正在做的事情有点奇怪：当你要求设置document.product_ids时，你实际在做的是在某些描述对象上设置匹配的document_id和product_id。对？这很奇怪，并且在意图/预期结果中非常不清楚。
那么替代方法是什么？您正在做的是向文档添加描述，这些描述在产品上。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，并且提供者更清晰，界面。