继承的类找不到表

Question

我有三个使用继承的模型，以及一个名为“telecom_circuits”的表。

class Telecom::Circuits::BaseCircuit < ActiveRecord::Base
end

class Telecom::Circuit < ::Telecom::Circuits::BaseCircuit
  ...
end

class Telecom::Circuits::AttVoiceCircuit < ::Telecom::Circuit
  self.table_name = 'telecom_circuits'
end

当我对继承的类进行创建时，它找不到表。

[1] pry(main)> Telecom::Circuits::AttVoiceCircuit
=> Telecom::Circuits::AttVoiceCircuit(id: integer, user_id: integer, division_id: integer, raw_site_id: integer, install_date: date, saville_account_number: string, account_number: string, meg8_account_number: string, main_circuit_id: string, d_channel: string, d_channel_type: string, ds3_access_circuit_id: string, lec_circuit_id: string, cli: string, lso: string, apn_ct1: string, dchan_cost: decimal, monthly_recurring_cost: decimal, created_at: datetime, updated_at: datetime, circuit_provision_type: string, trunk_group: string, apn_ct2: string, slot: string, disconnect_date: datetime, disconnect_requester_id: integer, disconnect_processor_id: integer, telecom_site_id: integer)
[2] pry(main)> Telecom::Circuits::AttVoiceCircuit.create
ActiveRecord::StatementInvalid: Mysql2::Error: Table 'itrc_dev.telecom_base_circuits' doesn't exist: SHOW FULL FIELDS FROM `telecom_base_circuits`
from /Users/mpierc200/.rvm/gems/ruby-1.9.3-p327@itrc/gems/activerecord-3.2.14/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:245:in `query'
[3] pry(main)> Telecom::Circuits::AttVoiceCircuit.table_name
=> "telecom_circuits"

如何让继承的类找到表？请记住，我将需要具有不同表的其他继承类。

Answer 1

这看起来像是 Rails 3.2 中的一个错误，即 fixed in Rails 4.0.0。

ETA：实际上，您可能需要add abstract class 来解决您当前的问题，但随后遇到了这个错误；）

另见此相关Documentation commit。

ETA 再次：A closed rails issue 听起来也相关；具有非抽象类和每类表的继承看起来不受支持。

Answer 2

这里有很多概念。 Ruby 继承、Rails STI 和命名空间。

首先，您似乎将 Ruby 的面向对象继承与 Rails 单表继承 (STI) 混淆了，因为它们都混淆了继承。然而，对于 STI，关键的要点是 single table 一词。 Rails STI 假设所有对象都将保存到一个表中，并且模型会将它们的类名添加到名为 type 的额外 db 列中。此列需要存在才能使 STI 正常工作。它还允许您通过它们的 class_name

获取它们

Telecom::Circuits::Base.all

或

Telecom::Circuits::AttVoice.all

我理解的你的代码应该是

# in app/telecom/circuit.rb
class Telecom::Circuit < ActiveRecord::Base
  ...
end

# in app/telecom/circuits/base.rb
class Telecom::Circuits::Base < Telecom::Circuit
  ...
end

# in app/telecom/circuits/att_voice.rb    
class Telecom::Circuits::AttVoice < Telecom::Circuit
  ... 
end

我冒昧地将 base 和 att_voice 设为电路的子类，因为我假设它们都是独立的电路类型。如果 base 具有其他子类共享和添加的功能，那么这个类是多余的，代码将进入 Telecom::Circuit 类。

如果这不是您想要的，那么您就超出了 Rails 中使用的 ActiveRecord 模型。您可能需要为每个人提供自己的完整表格。或者也许您可以利用DataMapper 或新的ROM 来实现您的目的。

希望这会有所帮助！

Answer 3

你不应该用 Rails 继承超过 1 个级别，它会变得复杂并且不能很好地工作。我有一个类似的结构，然后回到只有一个继承。

我不确定这是否有效，但您是否也尝试过：

class BaseCircuit < ActiveRecord::Base
end

class Circuit < BaseCircuit
  ...
end

class AttVoiceCircuit < Circuit
  ...
end

所以没有命名空间？表名应为“base_circuits”

编辑： 在有人建议的答案中，问题出在不止一层继承或命名空间上。我尝试了以下方法：

class BaseSo < ActiveRecord::Base
end

class AttVoice < BaseSo
  self.table_name = 'telecom_circuits'
end

class ComcastVoice < BaseSo
  self.table_name = 'telecom_pri_circuits'
end

这些结果：

[1]pry(main)> AttVoice
=> AttVoice(id: integer, user_id: integer, division_id: integer, raw_site_id: integer, install_date: date, saville_account_number: string, account_number: string, meg8_account_number: string, main_circuit_id: string, d_channel: string, d_channel_type: string, ds3_access_circuit_id: string, lec_circuit_id: string, cli: string, lso: string, apn_ct1: string, dchan_cost: decimal, monthly_recurring_cost: decimal, created_at: datetime, updated_at: datetime, circuit_provision_type: string, trunk_group: string, apn_ct2: string, slot: string, disconnect_date: datetime, disconnect_requester_id: integer, disconnect_processor_id: integer, telecom_site_id: integer)
[2] pry(main)> AttVoice.table_name
=> "telecom_circuits"
[3] pry(main)> ComcastVoice
=> ComcastVoice(id: integer, created_at: datetime, updated_at: datetime, order_submitter: string, division_id: integer, lead_id: integer, pin: integer, raw_site_id: integer, site_poc: string, install_date: date, csg_billing_number: string, gl_code: string, pri_count: integer, pri_type: string, port_native: boolean, did_range: string, did_count: integer, comments: string, telecom_site_id: integer)
[4] pry(main)> ComcastVoice.table_name
=> "telecom_pri_circuits"
[5] pry(main)> AttVoice.count
(41.8ms)  SELECT COUNT(*) FROM `telecom_circuits` 
=> 2247
[6] pry(main)> AttVoice.create
ActiveRecord::StatementInvalid: Mysql2::Error: Table 'itrc_dev.base_sos' doesn't exist: SHOW FULL FIELDS FROM `base_sos`
from /Users/mpierc200/.rvm/gems/ruby-1.9.3-p327@itrc/gems/activerecord-3.2.14/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:245:in `query'
[7] pry(main)> ComcastVoice.count
(0.4ms)  SELECT COUNT(*) FROM `telecom_pri_circuits` 
=> 155
[8] pry(main)> ComcastVoice.create
ActiveRecord::StatementInvalid: Mysql2::Error: Table 'itrc_dev.base_sos' doesn't exist: SHOW FULL FIELDS FROM `base_sos`
from /Users/mpierc200/.rvm/gems/ruby-1.9.3-p327@itrc/gems/activerecord-3.2.14/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:245:in `query'

Answer 4

模块和 mixin 会为您处理这个问题吗？

见here。