Demonstrates abstraction of columns via a method

active_record_example.rb

require 'rubygems'
require 'fileutils'
require 'active_record'

# >ruby active_record_example.rb 
# a
# b
# a.b
# x
# y
# x.y

class Example < ActiveRecord::Base
  def three
    [one, two].join('.')
  end
  
  def three=(value)
    one, two = value.split('.', 2)
    self.one = one
    self.two = two
  end
end

#
# Setup
#

database = 'example.sqlite3'
FileUtils.rm(database) if File.exists?(database)

ActiveRecord::Base.establish_connection(
  :adapter  => 'sqlite3',
  :database => database
)
connection = ActiveRecord::Base.connection.raw_connection
connection.execute %q{
  create table examples (
    id integer primary key,
    one varchar2(255),
    two varchar2(255)
  );
}

#
# Example
#

Example.create(:one => 'a', :two => 'b')

example = Example.find(:first)
puts example.one
puts example.two
puts example.three

# example.update_attributes({:three => 'x.y'})
example.attributes = {:three => 'x.y'}
example.save

example = Example.find(:first)
puts example.one
puts example.two
puts example.three