What is CouchResource ?¶ ↑

CouchResource is an ActiveRecord-style data mapper for CouchDB. You can develop model classes baed on the ActiveRecord way.

You can install from github,

gem source -a http://github.com
sudo gem install yssk22-couch_resource

And official gem packages is also available in WebJourney Project @RubyForge

version 0.9.0-incubating (currently installed from svn trunk).

• Automapping CouchDB database

CouchReSource model classes are automatically mapped to databases.

class MyDocument < CouchResource::Base
end
#=> mapped to http://localhost:5984/my_documents

You can set the specific database uri with set_database method.

class MyDocument < CouhcResource::Base
  set_database http://user:password@host:port/database1
end
#=> mapped to http://user:password@host:port/database1

• Typed attributes

CouchDB is schemaless so that you can set data attributes directly in your model code.

class MyDocument < CouhcResource::Base
  string :title
  string :content
  array  :tags, :is_a => String
end
doc = MyDocument.new
doc.title   = "My document"
doc.content = "My content..."

And you can use nested data structure using CouchResource::SubResource.

class Comment < CouchResource::SubResource
  string :content
end

class MyDocument < CouhcResource::Base
  string :title
  string :content
  array  :tags,     :is_a => String
  array  :comments, :is_a => Comment
end
doc = MyDocument.new
doc.comments = []
doc.comments << Comment.new(:content => "comment ... ")

• Validation with typed attributes

ActiveRecord-like validations are supported.

class MyDocument < CouhcResource::Base
  string :title, :validates => [[:length_of, {:in => 1..64, :allow_nil => false}]]
end

You can use validations indivisually out of attributes.

class MyDocument < CouhcResource::Base
  string :title
  validates_length_of :title, :in => 1..64, :allow_nil => false
end

• Callbacks

This feature is also the same as ActiveRecord.

class Person < CouchResource::Base
  string :credit_card_id
  def before_destroy # is called just before Person#destroy
    CreditCard.find(credit_card_id).destroy
  end
end

• Direct manipulation

  docId = “abcdefg” MyDocument.find(docId)

• Logging Support

  CouchResource::Base.logger = Logger.new(STDOUT) CouchResource::Base.logger = Log4r::Logger.new(“Application Log”)

• Observers

TBD, not implemented yet.

• Inheritance hierarchies

TBD, not implemented yet.

• Transactions

Not applicable for CouchDB.

• Reflections on columns, associations, and aggregations

Not applicable for CouchResource.

• MapReduce finders

  class MyDocument < CouchResource::Base

  string :title
  string :content
  array  :tags, :is_a => String
  
  # define finder method (find_by_{design_name}_{view_name}) using map/reduce scripts
  view :tags, :count => {
     :map    => include_js("path/to/map.js"),
     :reduce => include_js("path/to/reduce.js")
  }
  

  end

  MyDocument.find_tags_count(“web”)

• Pagination in finders

  class MyDocument < CouchResource::Base

  string :title
  string :content
  array  :tags, :is_a => String
  

  end

  docs = MyDocument.find(:all, :count => 3) # => first 3 documents in docs docs = MyDocument.find(docs) # => next 3 documents in docs (*1) docs = MyDocument.find(docs) # => next more 3 documents in docs docs = MyDocument.find(docs) # => backward 3 documents in docs (the same as *1)

To enable rails utilities in CouchResource, you may need to add the following sentences in your config/environment.rb.

require 'couch_resource'
require 'couch_resource/rails'

• CouchConfig

You can define multipe CouchDB sites in config/couchdb.yml and use the configurations in your CouchResource models.

development:
  user_profiles:
    host: localhost
    port: 5984
    database: user_profiles_development
  pages:
    host: localhost
    port: 5984
    database: pages_development
  feeds:
    host: localhost
    port: 5984
    database: feeds_development

class Page < CouchResource::Base
  set_database CouchConfig.database_uri_for(:db => :wj_pages)
end

• CouchFixture

Add followings in your test/test_helper.rb.

class Test::Unit::TestCase
  #  ... (snip) ...

  # Add more helper methods to be used by all tests here...
  setup :setup_couch_fixture
  def setup_couch_fixture
    CouchFixture.load
  end
end

Then You can define fixtures in test/fixtures/couchdb/{model_name}.yml

WebJourney and it’s blog component. Both of them are developed on github.com/yssk22/webjourney/tree/master

Let’s collabolate our project site or please fork the github repo at github.com/yssk22/couch_resource.

There are some useful alternatves for CouchDB mapper in Ruby environment.

CouchPotato : github.com/langalex/couch_potato/tree/master CouchRest : github.com/jchris/couchrest/tree/master

Copyright © 2009 Yohei Sasaki. See MIT_LICENSE for details.