[Ruby] ActiveRecord off Rails

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» Posted by ice on Jan 8, 2009 in Blog | 0 comments

How to use ActiveRecord without Rails.

Memo

Usually no need to write definition of database tables.
Just define sub class of ActiveRecord::Base.
ActiveRecord automatically checks table definition at the first access.
Better to use ActiveRecord’s naming rules
If name tables or fields without the naming rules, should add extra code into sub class of ActiveRecord::Base
Need to write SQL directory when do complicated stuff.
Access to table with sub class instance of ActiveRecord::Base

Basic Usage

Create database configuration YAML file
Create a sub class of ActiveRecord::Base for each table
Establish connection with the YAML file.
Do something with the sub class of ActiveRecord::Base

Simple Usage

#!/usr/bin/env ruby

# definition of 'groups' table
#CREATE TABLE IF NOT EXISTS groups (
#  id       INT(32) UNSIGNED NOT NULL AUTO_INCREMENT,
#  name     VARCHAR(255) NOT NULL,
#  PRIMARY KEY (id)
#) ENGINE=MyISAM;

require 'rubygems'
require 'activerecord'

# automatically map to 'groups' table.
class Group < ActiveRecord::Base
end # class

spec = {
  :adapter  => 'mysql',
  :encoding => 'utf8',
  :database => 'messadb_dev', # database name
  :username => 'messauser',   # username for mysql
  :password => 'messapass',   # password for mysql
  :socket   => '/var/run/mysqld/mysqld.sock',
}
ActiveRecord::Base.establish_connection(spec)

# create a record
group = Group.new
#group.id = 2
group.name = 'christmas town'
group.save

# find a record by it's name
group = Group.find_by_name('christmas town')
puts "group.id   : #{group.id}"   # 
puts "group.name : #{group.name}" # 'christmas town'

Sample Environment

database: mysql
dbnames:
  for production:  messadb
  for test:        messadb_test
  for development: messadb_dev
tables:
  table1: users
  table2: groups

Sample Directory Structure

activerecord-sample/
  app/
    messa_app.rb      # main program
  config/
    database.yml      # configuration file for database connection
  db/
    setup_dev.mysql   # script for initializing database
  lib/
    messa/
      db.rb           # Messa::DB::Base, a sub class of ActiveRecord::Base
      db/
        user.rb      # a sub class of Messa::DB::Base
        group.rb     # a sub class of Messa::DB::Base

Install requirements (Ubuntu 8.10 Intrepid Ibex)

% sudo aptitude install ruby rubygems
% sudo gem install activerecord
% sudo aptitude install libmysql-ruby

Setup and execute

% cd activerecord-sample
% mysql -u root -p
mysql> source db/setup_dev.mysql
mysql> exit
% ruby app/messa_app.rb

app/messa_app.rb

load Messa::DB::User and Messa::DB::Group sub classes of ActiveRecord::Base.

require 'messa/db'
require 'messa/db/user'
require 'messa/db/group'

load a YAML database configuration file, then set it to Messa::DB::Base and select configuration for development.

config_file = File.join(MESSA_CONFIG_DIR, 'database.yml')
config = YAML::load(ERB.new(IO.read(config_file)).result)
Messa::DB::Base.configurations = config
Messa::DB::Base.establish_connection(:messadb_development)
#Messa::DB::Base.establish_connection(:messadb_test)
#Messa::DB::Base.establish_connection(:messadb_production)

create a new group and save.

group = Messa::DB::Group.new
group.id = 1
group.name = 'halloween town'
group.save

create a new user and save.

user = Messa::DB::User.new
user.id   = 1
user.group_id   = 1
user.name = 'Jack'
user.birthday  = '1901-10-31'
user.save

find a user by id then print values.

jack = Messa::DB::User.find(1)
puts "jack.id         : #{jack.id}"         # 1
puts "jack.group_id   : #{jack.group_id}"   # 1
puts "jack.group.name : #{jack.group.name}" # 'halloween town'
puts "jack.name       : #{jack.name}"       # 'Jack'
puts "jack.birthday   : #{jack.birthday}"   # '19001-10-31'
puts "jack.age        : #{jack.age}"        # 107

Source Code

Download Source Code

messa_app.rb

#/usr/bin/env ruby
# -*- coding: utf-8 -*-

$LOAD_PATH << File.expand_path(File.join('..', 'lib'), File.dirname(__FILE__))

require 'messa/db'
require 'messa/db/user'
require 'messa/db/group'
require 'date'

MESSA_ROOT_DIR   = File.expand_path(File.join('..'), File.dirname(__FILE__)) unless defined? MESSA_ROOT_DIR
MESSA_CONFIG_DIR = File.join(MESSA_ROOT_DIR, 'config')                       unless defined? MESSA_CONFIG_DIR

config_file = File.join(MESSA_CONFIG_DIR, 'database.yml')
config = YAML::load(ERB.new(IO.read(config_file)).result)
Messa::DB::Base.configurations = config
Messa::DB::Base.establish_connection(:messadb_development)
#Messa::DB::Base.establish_connection(:messadb_test)
#Messa::DB::Base.establish_connection(:messadb_production)

Messa::DB::Group.delete_all
Messa::DB::User.delete_all

group = Messa::DB::Group.new
group.id = 1
group.name = 'halloween town'
group.save

user = Messa::DB::User.new
user.id   = 1
user.group_id   = 1
user.name = 'Jack'
user.birthday  = '1901-10-31'
user.save

user = Messa::DB::User.new
#user.id   = 2
user.group_id   = 1
user.name = 'Sarry'
user.birthday  = '1997-10-31'
user.save

puts "today : #{Date.today}" # 2009-01-06

jack = Messa::DB::User.find(1)
puts "jack.id         : #{jack.id}"         # 1
puts "jack.group_id   : #{jack.group_id}"   # 1
puts "jack.group.name : #{jack.group.name}" # 'halloween town'
puts "jack.name       : #{jack.name}"       # 'Jack'
puts "jack.birthday   : #{jack.birthday}"   # '19001-10-31'
puts "jack.age        : #{jack.age}"        # 107

sarry = Messa::DB::User.find(:first, :conditions => {:name => 'Sarry'})
puts "sarry.id         : #{sarry.id}"        # 
puts "sarry.group_id   : #{sarry.group_id}"  # 1
puts "sarry.group.name : #{jack.group.name}" # 'halloween town'
puts "sarry.name       : #{sarry.name}"      # 'Sarry'
puts "sarry.birthday   : #{sarry.birthday}"  # '1997-10-31'
puts "sarry.age        : #{sarry.age}"       # 11

__END__

today : 2009-01-06
jack.id         : 1
jack.group_id   : 1
jack.group.name : halloween town
jack.name       : Jack
jack.birthday   : 1901-10-31
jack.age        : 107
sarry.id         : 10
sarry.group_id   : 1
sarry.group.name : halloween town
sarry.name       : Sarry
sarry.birthday   : 1997-10-31
sarry.age        : 11

database.yml

messadb_development:
  adapter: mysql
  encoding: utf8
  database: messadb_dev
  username: messauser
  password: messapass
  socket: /var/run/mysqld/mysqld.sock

messadb_test:
  adapter: mysql
  encoding: utf8
  database: messadb_test

  username: messauser
  password: messapass
  socket: /var/run/mysqld/mysqld.sock

messadb_production:
  adapter: mysql
  encoding: utf8
  database: messadb
  username: messauser
  password: messapass
  socket: /var/run/mysqld/mysqld.sock

setup_dev.mysql

-- messadb

-- % mysql -u root -p
-- mysql> create database messadb;
-- mysql> source create_tables.mysql
-- mysql> exit

DROP DATABASE messadb_dev;

CREATE DATABASE IF NOT EXISTS messadb_dev DEFAULT CHARACTER SET utf8;
GRANT ALL PRIVILEGES ON messadb_dev.* TO messauser@localhost IDENTIFIED BY 'messapass';

use messadb_dev;

CREATE TABLE IF NOT EXISTS users (
  id       INT(32) UNSIGNED NOT NULL AUTO_INCREMENT,
  group_id INT(32) UNSIGNED NOT NULL,
  name     VARCHAR(255) NOT NULL,
  birthday DATE         NULL,
  added             TIMESTAMP    NOT NULL DEFAULT 0,
  updated           TIMESTAMP    NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  PRIMARY KEY (id)
) ENGINE=MyISAM;

CREATE TABLE IF NOT EXISTS groups (
  id       INT(32) UNSIGNED NOT NULL AUTO_INCREMENT,
  name     VARCHAR(255) NOT NULL,
  added             TIMESTAMP    NOT NULL DEFAULT 0,
  updated           TIMESTAMP    NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  PRIMARY KEY (id)
) ENGINE=MyISAM;

db.rb

# -*- coding: utf-8 -*-

require 'rubygems'
require 'activerecord'
require 'erb'
require 'yaml'

module Messa
  module DB
    class Base < ActiveRecord::Base
    end # class
  end # module
end # module

users.rb

# -*- coding: utf-8 -*-

require 'messa/db'
require 'date'

module Messa
  module DB
    class User < Messa::DB::Base
      set_table_name 'users'
      #has_one :group, {:class_name => 'Messa::DB::Group', :foreign_key => 'id'} # this works
      has_one :group, {:class_name => 'Messa::DB::Group', :foreign_key => 'id', :primary_key => 'group_id'}

      def age
        birthday = read_attribute(:birthday)
        return nil if birthday.nil?

        today = Date.today
        age = today.year - birthday.year
        if (today.month < birthday.month) or (birthday.month == today.month and today.day < birthday.day)
          age -= 1
        end
        return age
      end

      def age=(rhs)
        raise "Can't set value to age."
      end
    end # class
  end # module
end # module

groups.rb

# -*- coding: utf-8 -*-

require 'messa/db'

module Messa
  module DB
    class Group < Messa::DB::Base
      set_table_name 'groups'
    end # class
  end # module
end # module