Elasticsearch::Persistence::Model で Dynamic Attribute

class User
  include Elasticsearch::Persistence::Model

  def initialize(attrs = {})
    set_attributes(attrs)
    super attrs
  end

  def set_attributes(attrs = {})
    attrs.each do |attr, value|
      set_attribute(attr, value)
    end
  end

  def set_attribute(attribute, value)
    attribute = attribute.to_sym
    unless self.class.attribute_set.map { |attr| attr.name }.include? attribute
      self.class.attribute attribute, value.class
    end
    send "#{attribute.to_s}=", value
  end

  def []=(attribute, value)
    set_attribute(attribute, value)
  end

  def method_missing(meth, *args, &block)
    if meth.to_s =~ /(.+)=$/
      set_attribute($1, args.first)
    else
      super
    end
  end
end