Question

更新我的User模型时，我有一个更新credit字段的回调：

class User < ActiveRecord::Base
  around_update :adjust_credit

  ...

  def adjust_credit
    ...
    yield
    ...
    puts "LEAVING: credit was #{self.credit}"

    new_credit = self.credit - User.average_active
    puts "new credit =  #{new_credit}"

    success = self.update_attribute :credit, new_credit

    puts "AFTER SAVE CREDIT: #{User.find(self.id).credit}"
    puts "Successful? #{success}"

  end
end

出于某种原因，credit没有更新，正如控制台日志验证的那样：

#console log
LEAVING: credit was 40
new credit =  -25
AFTER SAVE CREDIT: 40
Successful? true

Answer 1

修改你的问题是，如果你在“就地”修改一个属性，这意味着：如果没有给它赋一个新的值，那么Rails会认为没有什么新的东西可以保存，所以它“优化”了保存。

试试这个：

def adjust_credit ... yield #saves ... puts "LEAVING: credit was #{self.credit}" new_credit = self.credit - User.average_active puts "new credit = #{new_credit}" self.credit = new_credit success = self.update_column(:credit, new_credit) puts "AFTER SAVE CREDIT: #{User.find(self.id).credit}" puts "Successful? #{success}" end

http://apidock.com/rails/ActiveRecord/Persistence/update_column

您应首先了解around_回调的流程。 around_*回调称为围绕操作以及before_*和after_*操作内部。例如：

class User def before_save puts 'before save' end def after_save puts 'after_save' end def around_save puts 'in around save' yield puts 'out around save' end end User.save before save in around save out around save after_save => true

有关回调的更多详情：http://api.rubyonrails.org/classes/ActiveRecord/Callbacks.html

via：Pan Thomakos

Answer 2

首先使用的原因是：

self.update_attribute(:credit, new_credit)
success = self.save

update_attribute已经保存了记录，self.save会让你感到困惑

success = self.update_attribute(:credit, new_credit)

我建议使用

self.update_column(:credit, new_credit)

不同的是update_column不会再次触发回调，但update_attribute将

Rails应用程序不在回调方法中保存字段

2 个答案: