Rails3.2.x で github/ripple を使う。

application.rb

require 'ripple/railtie'

# rails g ripple をして必要ファイルを生成すること

article.rb

class Article
  include Ripple::Document
  property :title, String
  property :body,  String, presence:true
  
  one :user
end

Gemfile

gem 'ripple', "~>1.0.0.beta2"

user.rb

class User
  include Ripple::Document
  property :name,  String
  property :login, String, presence:true
  
  index :login, String
  
  many :articles
end

z.rb

> u = User.create(name:'CHU', login:'chu')
=> <User:o8fmcna88jctpxghshj7j5oncr9 login="chu" name="CHU">
> u.articles < < Article.create(title:"Hello world")
=> <Article:rsfkusim2keemw62kmtwjbjzo7n title="Hello world" body=nil>
> u.save
=> true
> User.find('7MtYxfhCObVSBqPX7DlEQYA5rtY')
=> <User:o8fmcna88jctpxghshj7j5oncr9 login="chu" name="CHU">
> User.find_by_index(:login, 'chu')
=> [<User:o8fmcna88jctpxghshj7j5oncr9 login="chu" name="CHU">]