rails验证惟一性的失败很奇怪

Question

我有两种型号：

class PollAnswer < ActiveRecord::Base
  belongs_to :poll, inverse_of: :poll_answers
  # Validations
  validates :answer, presence: true, uniqueness: { scope: :poll_id, case_sensitive: false }
  validates :votes_number, presence: true
  validates :poll, presence: true
end
class Poll < ActiveRecord::Base
  # Associations
  has_many :poll_answers, inverse_of: :poll, dependent: :destroy
  # Attributes
  accepts_nested_attributes_for :poll_answers, reject_if: :all_blank, allow_destroy: true
  # Validations
  validates :question, presence: true
  validate :has_minimum_2_poll_answers
  private
  def has_minimum_2_poll_answers
    remaining_poll_answers = poll_answers.reject(&:marked_for_destruction?)
    if remaining_poll_answers.size < 2
      errors.add :poll_answers, I18n.t(:minimum_2_poll_answers, scope: "activerecord.errors.models.polls")
    end
  end
end

和一个简单的测试：

let(:new_poll_answer) { build(:poll_answer) }
let(:new_poll_answer1) { build(:poll_answer) }
let(:new_poll) { create(:poll) }
it "validates the uniqueness of an answer scoped to poll_id" do
  new_poll_answer.answer = "andre"
  new_poll_answer.poll = new_poll
  new_poll_answer1.answer = "andre"
  new_poll_answer1.poll = new_poll
  expect(new_poll_answer.valid?).to eq(false)
end

它失败了：

1) PollAnswer validations validates the uniqueness of an answer scoped to poll_id
     Failure/Error: expect(new_poll_answer.valid?).to eq(false)
   expected: false
        got: true
   (compared using ==)
 # ./spec/models/poll_answer_spec.rb:22:in `block (3 levels) in <top (required)>'
 # -e:1:in `<main>'

有什么想法吗？

更新：

在Marek Lipka评论之后，我可以看出这正是我的问题，因为accepts_nested_attributes_for就是这样工作的。因此它不验证唯一性。

我试过这个测试：

it "validates the uniqueness of an answer scoped to poll_id" do
  new_poll_answer.answer = "andre"
  new_poll_answer.poll = new_poll
  new_poll_answer1.answer = "andre"
  new_poll_answer1.poll = new_poll
  new_poll.save
  puts "#{new_poll.inspect}"
  puts "#{new_poll_answer.inspect}"
  puts "#{new_poll_answer1.inspect}"
  expect(new_poll_answer1.valid?).to eq(false)
end

我得到这个：

#<Poll id: 62, question: "Question", created_at: "2014-04-08 12:31:06", updated_at: "2014-04-08 12:31:06", active: true, published_at: "2014-04-08 11:31:06">
#<PollAnswer id: nil, answer: "andre", votes_number: 0, poll_id: 62, created_at: nil, updated_at: nil>
#<PollAnswer id: nil, answer: "andre", votes_number: 0, poll_id: 62, created_at: nil, updated_at: nil>
Failures:
  1) PollAnswer validations validates the uniqueness of an answer scoped to poll_id
     Failure/Error: expect(new_poll_answer1.valid?).to eq(false)
       expected: false
            got: true
       (compared using ==)

如果你看看我为名为has_minimum_2_poll_answers的轮询类进行的自定义验证，这对我来说仍然很奇怪。

只有在没有具有相同答案的poll_answers的情况下，我才能正确验证是否应该创建民意调查？

Answer 1

您没有保存第一个new_poll_answer，唯一性验证对未保存的记录无效。你需要做：

new_poll_answer.save

在测试CCD_ 2的有效性之前。

Answer 2

还要注意，除了要求其中一条记录之前已保存之外，不可能保证在应用层中进行唯一性验证。唯一性验证只能使用数据库层约束（即唯一索引）来保证。

Rails文档摘录：

并发性和完整性

将此验证方法与ActiveRecord:：Validations#save结合使用并不能保证不存在重复的记录插入，因为应用程序级别的唯一性检查天生就容易出现竞争条件。例如，假设两个用户试图同时发布一个Comment，并且Comment的标题必须是唯一的。在数据库级别，这些用户执行的操作可以按以下方式交错：