README.markdown

Rdb4o

see http://teamon.github.com/rdb4o

Author: Kacper Cieśla, Tymon Tobolski

Small library I wrote for fun too have even more fun with db4o and jruby :) Lots of thanks for Marcin Mielżyński (lopex) for helping me with this.

Requirements

All you need to use rdb4o is JRuby 1.2.0.

Getting started

git clone git://github.com/teamon/rdb4o.git
cd rdb4o
rake install

Usage

Model file

# app/models/cat.rb
class Cat
  include Rdb4o::Model

  field :name, String
  field :age, Fixnum
end

Generate and compile

rdb4o generate app/models
rdb4o compile app/models

Require rdb4o

require 'rubygems'
require 'rdb4o'

Load models

Rdb4o.load_models
Dir["app/models/*.rb"].each {|f| require f }

Connect to database

Rdb4o::Database.setup :dbfile => 'simple.db'

Create some objects

Cat.create(:name => "Kitty", :age => 2)
Cat.create(:name => "Foobar", :age => 1)

Get them from database

Cat.all

Close database

This step is not necessary - database gets closed automaticly when process ends. Rdb4o::Database.close

Run program

Due to classpaths issue the best way to run this program is to use rdb4o executable. rdb4o run main.rb

Relations

One to Many

class Cat
  include Rdb4o::Model

  field :name, String
  field :age, Fixnum

  belongs_to :person
  belongs_to :owner, :class => Person
end

class Person
  include Rdb4o::Model

  field :name, String

  has_many :cats
  has_many :friends, :class => Cat, :key => :owner
end

p = Person.create(:name => "Foo")
c = Cat.new

p.cats 
p.cats.new
p.cats.create

c = Cat.new
p.cats << c
p.cats.delete(c)
p.cats.destroy_all!

c.person = p

Filtering

Cat.all # all objects
Cat.all(:name => "Kitty") # all cats with name "Kitty"
Cat.all{|c| c.age > 1 } # cats older than 1 year
# etc.

Scope

class Cat
  scope(:young) {|c| c.age <= 2}
  scope(:old) {|c| c.age > 4}
  scope :black, :color => "black"
  scope :white, :color => "white"
  scope(:colorful) {|c| c.color != "black" && c.color != "white"}
  scope(:four_letters) {|c| c.name.size == 4}
  scope :kitties, :name => "Kitty"
end

Cat.young
Cat.old
Cat.kitties.black.young

# works with relations

p = Person.create(:name => "Eric")

p.cats.black
p.cats.black.old.new

Ordering

Cat.all.order(:name.desc)
Cat.all.order(:name.asc, :age.desc)
Cat.all.order {|a,b| a.name.size <=> b.name.size }