How to get attribute of a model saved in instance variable

I am writing a plugin, in which i define a new relation dynamically within plugin. Sample code is given below

module AttachDocumentsAs
   @as = nil
   def attach_documents_as(*attachment_as)
      attachment_as = attachment_as.to_a.flatten.compact.map(&:to_sym)
      @as           = attachment_as.first
      class_inheritable_reader(@as)

      class_eval do
          has_many @as, :as => :attachable, :class_name=>"AttachDocuments::Models::AttachedDocument"
          accepts_nested_attributes_for @a开发者_如何转开发s
      end 
   end
end

now in any model i used it as

class Person < AtiveRecord::Base
    attach_documents_as :financial_documents
end

Now want to access want to access this attribute of the class in overloaded initialize method like this

def initialize(*args)
   super(*args)
   "#{@as}".build 
end

But it is not getting required attribute, can any one help me in it. I want to build this relation and set some initial values.

Waiting for guidelines from all you guys.

You're likely confusing the @as class instance variable, which is only available to class methods for Person, and the @as instance variable, which is only available to instances of this class. Even that explanation sounds a bit complicated, I know.

Each object has instance variables, and a class is simply a type of object. Instances of this class are also objects and they have their own independent instance variables. To get a class instance variable from an instance of a class you will need a reader method, like you've defined. Maybe what you mean is:

def initialize(*args)
  super(*args)

  # self.class.as returns something like :financial_documents, so use this method
  # to return a scope to build in.
  send(self.class.as).build
end

The way you're using @as suggests you're used to something like PHP or Perl where you can de-reference it like you might with ${$as}. In Ruby you're usually de-referencing from a string or symbol into either a class, or a method.

It looks like you're trying to convert a symbol into a method call, and that's done through send.

If you were trying to convert a string into a class, you use the constantize method on String, a feature of the Rails environment.