Rails 4：.save 不会更新现有记录的updated_at？

我一直以为.save and .save!将更新updated_at现有记录列。这不是真的吗？如果是这样，那么我是否需要创建一个 before_save 过滤器以在每次保存时更新它？

今天是 6 月 18 日：

    Loading development environment (Rails 4.1.1)
    irb(main):001:0>  o = Order.last
      Order Load (0.4ms)  SELECT  `orders`.* FROM `orders`   ORDER BY `orders`.`id` DESC LIMIT 1
    => #<Order id: 24, user_id: 1, order_date: nil, total_cents: 0, total_currency: "USD", shipping_cents: 0, shipping_currency: "USD", tax_cents: 0, tax_currency: "USD", subtotal_cents: 0, subtotal_currency: "USD", created_at: "2014-06-13 21:24:38", updated_at: "2014-06-13 21:24:38", status: "Incomplete", coupon_id: nil>
    irb(main):002:0> o.save!
       (0.4ms)  BEGIN
       (0.3ms)  COMMIT
    => true
    irb(main):003:0> o.updated_at
    => Fri, 13 Jun 2014 21:24:38 UTC +00:00
    irb(main):004:0> o.reload
      Order Load (0.7ms)  SELECT  `orders`.* FROM `orders`  WHERE `orders`.`id` = 24 LIMIT 1
    => #<Order id: 24, user_id: 1, order_date: nil, total_cents: 0, total_currency: "USD", shipping_cents: 0, shipping_currency: "USD", tax_cents: 0, tax_currency: "USD", subtotal_cents: 0, subtotal_currency: "USD", created_at: "2014-06-13 21:24:38", updated_at: "2014-06-13 21:24:38", status: "Incomplete", coupon_id: nil>
    irb(main):005:0> o.updated_at
    => Fri, 13 Jun 2014 21:24:38 UTC +00:00

我关心这个的原因是因为我用以下内容包装了函数的内部ActiveRecord::Base.transaction所以我想测试一下当出现问题时它们不会更新：

Rspec 测试（在不应该的情况下总是通过，因为无论成功还是失败，updated_at 都不会改变）：

  it "rollsback the transaction" do
    ...
    order.stub(:save!).and_raise(StandardError)
    expect { payment_info.save }.not_to change { [billing_address.updated_at, 
                                                  shipping_address.updated_at,
                                                  order.user.updated_at,
                                                  order.updated_at] }
  end

还有我的方法：

def process_billing_info!
  ActiveRecord::Base.transaction do
    billing_address.save!
    shipping_address.save!
    user.save!
    order.update_all_fees!
  end
rescue Exception => e
  false
end

正如您在日志中看到的那样，没有UPDATE执行的 SQL 查询。 Rails 根本不会更新你的记录。这是因为.save实际上仅在发生更改时保存记录.

有方法.touch (文档 https://apidock.com/rails/ActiveRecord/Persistence/touch）您可以调用它来更新updated_at字段而无需更改您的记录：

1.9.3p489 :005 > Intervention.first.touch
  Intervention Load (12.9ms)  SELECT "interventions".* FROM "interventions" LIMIT 1
  SQL (20.5ms)  UPDATE "interventions" SET "updated_at" = '2014-06-18 16:34:03.924648' WHERE "interventions"."id" = 1
 => true 

在这里我们看到UPDATESQL 查询。