Curator

See Untangle Domain and Persistence Logic with Curator for the announcement blog post.

Curator is a model and repository framework for Ruby. It's an alternative to ActiveRecord-like libraries where models are tightly coupled to persistence. Curator allows you to write domain object that are persistence free, and then write repositories that persist these objects. These ideas are largely taken from the Repository section of Domain Driven Design.

Currently, curator supports Riak for persistence. If you are interested in enhancing curator to support other data stores, please let me know.

Usage

Domain objects should include the Curator::Model module:

class Note
  include Curator::Model
  attr_accessor :id, :title, :description, :user_id
end

These models can be intiatiated with hashes and used just like regular ruby objects:

note = Note.new(:title => "My Note", :description => "My description")
puts note.description

Repositories should include the Curator::Repository module:

class NoteRepository
  include Curator::Repository
  indexed_fields :user_id
end

Repositories have save, find_by_id, and find_by methods for indexed fields:

note = Note.new(:user_id => "my_user")
NoteRepository.save(note)

NoteRepository.find_by_id(note.id)
NoteRepository.find_by_user_id("my_user")

Fields included in indexed_fields automatically get a secondary index when persisted to Riak.

Rails

See curator_rails_example for an example application using curator.

If you use curator within Rails, all you need is to add curator to your Gemfile and create a config/riak.yml with contents like:

development:
  :http_port: 8098
  :host: localhost
test:
  :http_port: 8098
  :host: localhost

We recommend putting your models in app/models and your repositories in app/repositories. If you do this, don't forget to add app/repositories to the list of autoload paths:

# config/application.rb

config.autoload_paths += %W(#{config.root}/app/repositories)

You can also use Rails form builder with curator models:

<%= form_for @note, :url => { :action => "create" } do |f| %>
  <dl>
    <dt><%= f.label :title %></dt>
    <dd><%= f.text_field :title %></dd>
    <dt><%= f.label :description %></dt>
    <dd><%= f.text_area :description, :size => "60x12" %></dd>
  </dl>
  <%= f.submit "Create" %>

Without Rails

If you are not using Rails, you can configure curator manually:

Curator.configure(:riak) do |config|
  config.environment = "development"
  config.riak_config_file = File.dirname(__FILE__) + "/config/riak.yml"
end

Under the hood

Curator. The value is a json representation of the instance_values of the object. Your repository can implement serialize/deserialize to get different behavior.

The bucket name in riak is <bucket_prefix>:<environment>:<collection>. The bucket prefix is configurable. By default, it will either be curator or the name of the Rails application if you are using curator within Rails. The collection is derived from the name of the Repository class, and it can be overriden. For example, if you implement a NoteRepository, the riak bucket will be curator:development:notes in development mode, and curator:production:notes in production mode.