ruby-on-rails - 如何在所有模型上添加 has_many 关联

Question

现在我有一个初始化程序可以执行此操作:

ActiveRecord::Base.send :has_many, :notes, :as => :notableActiveRecord::Base.send :accepts_nested_attributes_for, :notes

它很好地建立了关联，除了当我加载一个使用它的 View 时，第二次加载给了我:不能复制 NilClass来自:

/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/base.rb:2184:in `dup'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/base.rb:2184:in `scoped_methods'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/base.rb:2188:in `current_scoped_methods'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/base.rb:2171:in `scoped?'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/base.rb:2439:in `send'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/base.rb:2439:in `initialize'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/reflection.rb:162:in `new'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/reflection.rb:162:in `build_association'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/associations/association_collection.rb:423:in `build_record'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/associations/association_collection.rb:102:in `build'
(my app)/controllers/manifests_controller.rb:21:in `show'

有什么想法吗？我做错了吗？有趣的是，如果我将关联移动到我正在使用的模型上，我不会收到此错误。我想我一定是错误地建立了全局协会。

Answer 1

您声明您有很多模型，所有模型都需要这种关联。如果是我，我会采用创建包含关联的基本模型类的方法，然后让所有其他模型继承它。像这样的东西:

class NotableModel < ActiveRecord::Base

  # Prevents ActiveRecord from looking for a database table for this class
  self.abstract_class = true

  has_many :notes, :as => :notable
  accepts_nested_attributes_for :notes  
end

class Foo < NotableModel
  ...
end

class Bar < NotableModel
  ...
end

在我看来，与使用隐藏在初始化程序中的一点点元编程相比，这种方法更易于 self 记录。