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

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

  field :name, String
  field :age, Fixnum
end

jrodb generate app/models
jrodb compile app/models

require 'rubygems'
require 'jrodb'

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

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

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

Cat.all

class Cat
  include Jrodb::Model

  field :name, String
  field :age, Fixnum

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

class Person
  include Jrodb::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

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.

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

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