gistfile1.rb

class User < ActiveRecord::Base
  def merge(other)
    %w{
      attribute_1
      attribute_2
      attribute_3
      attribute_4
      attribute_5
      attribute_6
    }.each do |attribute|
      self.write_attribute(attribute, oldest(attribute, other))
    end
    %w{
      attribute_7
      attribute_8
      attribute_9
    }.each do |attribute|
      self.write_attribute(attribute, first_non_blank(attribute, other))
    end

    # Unrelated code here ...
  end

private
  def oldest(attribute, other)
    oldest ||= created_at < other.created_at ? self : other
    oldest.send(attribute)
  end
  
  def first_non_blank(attribute, other)
    value = self.send(attribute)
    value.blank? ? other.send(attribute) : value
  end
end