从回调方法中叠加得太深

Question

我有四种运动模式，黄金，银牌和青铜，一对一的关系，体育和其他三种。运动的每一个实例都必须有一个金色、银色和青铜的实例，其中三个是使用运动模型中的回调函数创建的。这些回调函数是一个抛出我能够跟踪的错误的函数，因为生成的rails错误堆栈只是一行。

我的密码

模型

运动

class Sport < ActiveRecord::Base
    validates :sportname, presence: true, 
                         uniqueness: { case_sensitive: false }

   has_one :gold, inverse_of: :sport, :dependent => :destroy
   has_one :silver, inverse_of: :sport, :dependent => :destroy
   has_one :bronze, inverse_of: :sport, :dependent => :destroy

   accepts_nested_attributes_for :gold
   accepts_nested_attributes_for :silver
   accepts_nested_attributes_for :bronze


   after_validation :build_default_medals, on: :create

   def build_default_medals
    self.build_gold
    self.build_silver
    self.build_bronze
  end
end

黄金

class Gold < ActiveRecord::Base

  belongs_to :sport    #, inverse_of: :gold
  validates_associated :sport, presence: true

  belongs_to :team, inverse_of: :golds, counter_cache: true 
  validates_associated :team,  :if => :create, allow_nil: true  

  accepts_nested_attributes_for :team
  accepts_nested_attributes_for :sport
end

银牌

class Silver < ActiveRecord::Base

  belongs_to :sport   #, inverse_of: :silver   
  validates_associated :sport, presence: true

  belongs_to :team, inverse_of: :silvers, counter_cache: true 
  validates_associated :team, :if => :create, allow_nil: true    

  accepts_nested_attributes_for :team
  accepts_nested_attributes_for :sport
end

青铜

class Bronze < ActiveRecord::Base
  belongs_to :sport   #, inverse_of: :bronze
  validates_associated :sport, presence: true

  belongs_to :team, inverse_of: :bronzes, counter_cache: true 
  validates_associated :team,  :if => :create, allow_nil: true 

  accepts_nested_attributes_for :team
  accepts_nested_attributes_for :sport
 end

回调after_validation :build_default_medals, on: :create就是错误所在，在我的日志中产生了这个错误。

 Started POST "/admin/sports" for 127.0.0.1 at 2016-07-14 14:52:22 -0400
 Processing by Admin::SportsController#create as HTML
 Parameters:{"utf8"=>"√",authenticity_token"=>"jss1O4bSJd3hcqxuSpu/KAxaowB7d
g5pLZw55oGDf1M=", "sport"=>{"sportname"=>"boxing"}, "commit"=>"Create Sport"}
User Load (1.0ms)  SELECT  `users`.* FROM `users`  WHERE `users`.`id` = 1       LIMIT 1  (0.0ms)  BEGIN
Sport Exists (1.0ms)  SELECT  1 AS one FROM `sports`  WHERE `sports`.`sportname` = 'boxing' LIMIT 1
SQL (1.0ms)  INSERT INTO `sports` (`created_at`, `sportname`, `updated_at`) VALUES ('2016-07-14 18:52:22', 'boxing', '2016-07-14 18:52:22')
SQL (15.1ms)  UPDATE `sports` SET `created_at` = '2016-07-14 18:52:22', `id` = 13, `sportname` = 'boxing', `updated_at` = '2016-07-14 18:52:22' WHERE `sports`.`id` = 13
SQL (1.0ms)  INSERT INTO `golds` (`created_at`, `sport_id`, `updated_at`) VALUES ('2016-07-14 18:52:22', 13, '2016-07-14 18:52:22')
SQL (1.0ms)  UPDATE `sports` SET `created_at` = '2016-07-14 18:52:22', `id` =13, `sportname` = 'boxing', `updated_at` = '2016-07-14 18:52:22' WHERE `sports`.`id` = 13
SQL (1.0ms)  INSERT INTO `silvers` (`created_at`, `sport_id`, `updated_at`) VALUES ('2016-07-14 18:52:22', 13, '2016-07-14 18:52:22')
SQL (1.0ms)  UPDATE `sports` SET `created_at` = '2016-07-14 18:52:22', `id` =13, `sportname` = 'boxing', `updated_at` = '2016-07-14 18:52:22' WHERE `sports`.`id` = 13
SQL (1.0ms)  INSERT INTO `bronzes` (`created_at`, `sport_id`, `updated_at`) VALUES ('2016-07-14 18:52:22', 13, '2016-07-14 18:52:22')  (72.2ms)  
ROLLBACK
Completed 500 Internal Server Error in 213ms

SystemStackError (stack level too deep):  actionpack (4.1.8) lib/action_dispatch/middleware/reloader.rb:79


Rendered C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/actionpack-4.1.8/lib/action_dispatch/middleware/templates/rescues/_source.erb (2.0ms)
Rendered C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/actionpack-4.1.8/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb (4.0ms)
Rendered C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/actionpack-4.1.8/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb (7.0ms)
Rendered C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/actionpack-4.1.8/lib/action_dispatch/middleware/templates/rescues/diagnostics.erb within rescues/layout (145.1ms)

我很好奇为什么回调会在插入后触发更新，以及究竟是什么触发了ROLLBACK和Stack Level Too Deep的无限循环。任何洞察力都是值得赞赏的。谢谢。

编辑

使用after_create :build_default_medals代替after_validation :build_default_medals, on: :creation产品

  Started POST "/admin/sports" for 127.0.0.1 at 2016-07-14 16:19:24 -0400
  Processing by Admin::SportsController#create as HTML
  Parameters: {"utf8"=>"√","authenticity_token"=>"3LrwB6+nD9PJ9EwxEgIGhN3rVHP3UPLOHUz9MXWRJ4Y=", "sport"=>{"sportname"=>"dancing"}, "commit"=>"Create Sport"}
  User Load (1.0ms)  SELECT  `users`.* FROM `users`  WHERE `users`.`id` = 1 LIMIT 1   (0.0ms)  BEGIN
  Sport Exists (1.0ms)  SELECT  1 AS one FROM `sports`  WHERE `sports`.`sportname` = 'dancing' LIMIT 1
  SQL (1.0ms)  INSERT INTO `sports` (`created_at`, `sportname`,`updated_at`) VALUES ('2016-07-14 20:19:24', 'dancing', '2016-07-14 20:19:24') 
 Gold Load (2.0ms)  SELECT  `golds`.* FROM `golds`  WHERE `golds`.`sport_id` =8 LIMIT 1
 Silver Load (1.0ms)  SELECT  `silvers`.* FROM `silvers`  WHERE `silvers`.`sport_id` = 8 LIMIT 1
 Bronze Load (1.0ms)  SELECT  `bronzes`.* FROM `bronzes`  WHERE `bronzes`.`sport_id` = 8 LIMIT 1
 (45.5ms)  COMMIT

用于undefined method 'create' for #<Gold:0x63bf820>的编辑

def build_default_medals
  #Gold.create(sport: self, team: nil)
  #Silver.create(sport: self, team: nil)
  #Bronze.create(sport: self, team: nil)
  self.create_gold(team: nil)
  self.create_silver(team: nil)
  self.create_bronze(team: nil)
end

Answer 1

替换

after_validation :build_default_medals, on: :create

使用

after_create :build_default_medals

你正在尝试建立相关的模型，而运动仍然是一个新的记录，而不是一个持久化的记录。validates_associated :sport, presence: true会导致循环依赖，并会产生错误。

我复制并测试了这一变化。会很好的。

对于保存的对象，请使用self.create_gold而不是self.build_gold，如下所示

  def build_default_medals
    self.create_gold
    self.create_silver
    self.create_bronze
  end

同时去除黄金，银和青铜模型的accepts_nested_attributes_for :sport。参考- https://github.com/rails/rails/issues/7809