不直接从ActiveRecord::Base派生的Cant访问模型

Question

我已将Rails 2.3.14项目转换为Rails 3.2.2我在使用不直接从ActiveRecord::Base 下降的表格时遇到问题

我有一个定义如下的模型：

class PauaServiceTable < ActiveRecord::Base
    def self.abstract_class?
       true
    end
    ..
    ..
 end

我有许多班是从这个班派生出来的。例如：

 class Lookup < PauaServiceTable
    ...
 end

在Rails console (3.3.2)中，我可以实例化任何直接从Activerecord::Base继承的表，但任何从PauaServiceTable继承的表都会因以下堆栈跟踪而失败：

Loading development environment (Rails 3.2.2)
ruby-1.8.7-p334 :001 > l=Lookup.new
ActiveRecord::StatementInvalid: Mysql2::Error: Incorrect table name '': SHOW FULL FIELDS FROM ``
    from /Users/george/.rvm/gems/ruby-1.8.7-p334@rails322/gems/activerecord-3.2.2/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:243:in `query'
    from /Users/george/.rvm/gems/ruby-1.8.7-p334@rails322/gems/activerecord-3.2.2/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:243:in `execute'
    from /Users/george/.rvm/gems/ruby-1.8.7-p334@rails322/gems/activerecord-3.2.2/lib/active_record/connection_adapters/abstract_adapter.rb:280:in `log'
    from /Users/george/.rvm/gems/ruby-1.8.7-p334@rails322/gems/activesupport-3.2.2/lib/active_support/notifications/instrumenter.rb:20:in `instrument'
    from /Users/george/.rvm/gems/ruby-1.8.7-p334@rails322/gems/activerecord-3.2.2/lib/active_record/connection_adapters/abstract_adapter.rb:275:in `log'
    from /Users/george/.rvm/gems/ruby-1.8.7-p334@rails322/gems/activerecord-3.2.2/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:243:in `execute'
    from /Users/george/.rvm/gems/ruby-1.8.7-p334@rails322/gems/activerecord-3.2.2/lib/active_record/connection_adapters/mysql2_adapter.rb:211:in `execute'
    from /Users/george/.rvm/gems/ruby-1.8.7-p334@rails322/gems/activerecord-3.2.2/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:257:in `execute_and_free'
    from /Users/george/.rvm/gems/ruby-1.8.7-p334@rails322/gems/activerecord-3.2.2/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:424:in `columns'
    from /Users/george/.rvm/gems/ruby-1.8.7-p334@rails322/gems/activerecord-3.2.2/lib/active_record/connection_adapters/schema_cache.rb:12:in `initialize'
    from /Users/george/.rvm/gems/ruby-1.8.7-p334@rails322/gems/activerecord-3.2.2/lib/active_record/model_schema.rb:228:in `call'
    from /Users/george/.rvm/gems/ruby-1.8.7-p334@rails322/gems/activerecord-3.2.2/lib/active_record/model_schema.rb:228:in `default'
    from /Users/george/.rvm/gems/ruby-1.8.7-p334@rails322/gems/activerecord-3.2.2/lib/active_record/model_schema.rb:228:in `[]'
    from /Users/george/.rvm/gems/ruby-1.8.7-p334@rails322/gems/activerecord-3.2.2/lib/active_record/model_schema.rb:228:in `columns'
    from /Users/george/.rvm/gems/ruby-1.8.7-p334@rails322/gems/activerecord-3.2.2/lib/active_record/model_schema.rb:243:in `column_defaults'
    from /Users/george/.rvm/gems/ruby-1.8.7-p334@rails322/gems/activerecord-3.2.2/lib/active_record/base.rb:479:in `initialize'
    from (irb):1:in `new'
    from (irb):1ruby-1.8.7-p334 :002 > 

此代码在Rails 2.3.14中运行良好，但在转换为3.2.2后现在失败了。

Answer 1

尝试在class PauaServiceTable 中设置@abstract_class = true

---编辑

由于某些原因，table_name为空，请尝试以下操作：

class Lookup < PauaServiceTable
  set_table_name 'lookups'
end

我可以用这个代码重现你的错误：

class PauaServiceTable < ActiveRecord::Base
  def self.abstract_class?
    true
  end
end
class Lookup < PauaServiceTable
end

但是，以下工作：

class PauaServiceTable < ActiveRecord::Base
  @abstract_class = true
end
class Lookup < PauaServiceTable
end

l= Lookup.new
+----+------------+------------+
| id | created_at | updated_at |
+----+------------+------------+
|    |            |            |
+----+------------+------------+

Answer 2

PauaServiceTable和Lookup模型是否用于单个表？

如果是这样的话，那么PauaServiceTable模型应该有表名，Lookup表应该自动得到它。你也可以看看Single Table Inheritance。

如果不是，则意味着两个模型用于两个表，为什么Lookup要继承PauaServiceTable？您可能需要在这两个model之间建立关系（has_many、has_one等）。

Answer 3

对于Rails3.2.1+，我相信您想要

class PauaServiceTable < ActiveRecord::Base
  self.abstract_class = true
end

请参阅ActiveRecord:：继承：：ClassMethods