你如何用ruby把self传给class\u eval?

class SomeClass &lt ActiveRecord::Base
    has_many :join_models, :dependent=>:destroy
end

class JoinModel &lt ActiveRecord::Base
  belongs_to :some_class
  belongs_to :entity, :polymorphic=>true
end

module Foo
 module ClassMethods
   def acts_as_entity
      has_many :join_models,  :as=>:entity, :dependent=>:destroy
      has_many :some_classes,  :through=>:join_models

      klass = self.name.tableize
      SomeClass.class_eval "has_many :#{klass}, :through=>:join_models"
   end
  end
end

我想消除 klass= 行,但不知道如何传递引用 self 从召唤类进入 class_eval

有什么建议吗?