Question

我有2个型号：

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>'

任何想法为什么？

更新：

在Marek Lipka评论之后，我可以看到这正是我的问题，因为这就是accepts_nested_attributes_for的工作原理。所以它不会验证唯一性。

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

我得到了这个：

#<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 ==)

如果您查看名为has_minimum_2_poll_answers的poll类的自定义验证，对我来说仍然很奇怪。

我怎样才能正确验证只有在没有poll_answers具有相同答案的情况下才能创建民意调查？

Answer 1

您没有保存第一个new_poll_answer，唯一性验证不会对未保存的记录起作用。你需要这样做：

new_poll_answer.save

在测试new_poll_answer1之前的有效性。

Answer 2

另请注意，除了先前已保存其中一条记录的要求之外，无法保证应用程序层中的唯一性验证。只能使用数据库层约束（即唯一索引）来保证唯一性验证。

摘自Rails文档：

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本质上容易出现竞争条件。例如，假设两个用户尝试同时发布评论，并且评论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进行交错：

rails验证唯一性是奇怪的失败

2 个答案:

并发性和完整性