ruby-on-rails - Attr_accessor 和子类

Question

我有用户模型和两个子类 Developer 和 Buyer（子模型）。在每个模型中，我都有恒定的字段。

在模型用户

class User < ActiveRecord::Base
  attr_accessor *:get_fields

  after_initialize :get_additional_fields

  # FIELDS for current class
    def self.get_fields
      Object.const_get( self.name )::FIELDS
    end

  # set additional fields
  #
    def get_additional_fields
      self.country = 'text'
    end
end

我有一些错误NoMethodError: undefined methodcountry=' for #<Developer:

我的错误是什么？

更新

class Buyer < User
  FIELDS = [ :country, :avatar ]
end

class Developer < User
  FIELDS = [ :country, :avatar, :location, :first_name, :last_name ]
end

我的请求d = Developer.first