Rails的after_save回调未触发。

Question

我有以下的代码，对于删除记录来说非常有效，但是尝试使用after_save回调将记录插入表中却没有任何反应。

本质上，我正在创建一系列高级关系，应该创建或删除与campaign_category_metro_bids表相关的关系。如果在PHPMyAdmin中运行，则没有问题。但是在Rails中点击并激活只允许调用第二个回调，即after_destroy...

 class CampaignMetro < ActiveRecord::Base

    belongs_to :campaign
    belongs_to :metro

    after_destroy :destroy_category_campaign_metro_bid
    after_save    :create_category_campaign_metro_bid

    def create_category_campaign_metro_bid
        insert = "INSERT INTO campaign_category_metro_bids (campaign_id,category_id, metro_id, created_at, updated_at)
                    SELECT e.campaign_id, e.category_id, e.metro_id, NOW(), NOW()
                    FROM
                    (SELECT c.campaign_id, c.category_id, c.metro_id
                     FROM (SELECT a.campaign_id, a.category_id, b.metro_id
                           FROM campaign_categories a 
                           cross join campaign_metros b 
                           ON a.campaign_id = b.campaign_id) c) e
                    LEFT JOIN campaign_category_metro_bids d
                    ON d.campaign_id = e.campaign_id and
                       d.category_id = e.category_id and
                       d.metro_id    = e.metro_id
                    WHERE d.campaign_id is null and 
                          d.category_id is null and 
                          d.metro_id    is null;"

        ActiveRecord::Base.connection.execute(insert)
    end

    def destroy_category_campaign_metro_bid
        delete="DELETE d.*
                FROM campaign_category_metro_bids d
                LEFT JOIN
                (SELECT c.campaign_id, c.category_id, c.metro_id
                 FROM (SELECT a.campaign_id, a.category_id, b.metro_id
                       FROM campaign_categories a 
                       cross join campaign_metros b 
                       ON a.campaign_id = b.campaign_id) c) e
                ON d.campaign_id = e.campaign_id and
                   d.category_id = e.category_id and
                   d.metro_id    = e.metro_id
                WHERE e.campaign_id is null and 
                      e.category_id is null and 
                      e.metro_id    is null;"

        ActiveRecord::Base.connection.execute(delete)
    end
end

我该怎么让这个工作起来？

- Sauron

Answer 1

问题在于，在after_save时，将在数据库中创建记录的事务尚未提交，因此记录尚不存在。您需要使用after_commit。

http://apidock.com/rails/ActiveRecord/Transactions/ClassMethods/after_commit

- rafb3

---

我尝试过了，但没有成功。我正在使用回调函数来处理通过SQL调用创建的表格，而不是使用Active Record。 - Sauron

你能在该模型中获取任何保存/提交后回调函数吗？如果这是通过将地铁加入到广告系列或反之而创建的，则这将是问题所在，我们可以探索解决方案。 - rafb3

我将整个过程移植到使用 Active Record 创建的模型中，现在运行得非常顺利，没有任何问题。 - Sauron

这些模型是否与 has_and_belongs_to_many 相关？如果是的话，您可以尝试使用 has_many :through。http://guides.rubyonrails.org/association_basics.html#the-has-many-through-association - rafb3