Virtus
This is a partial extraction of the DataMapper Property API with various modifications and improvements. The goal is to provide a common API for defining attributes on a model so all ORMs/ODMs could use it instead of reinventing the wheel all over again. It is also suitable for any other usecase where you need to extend your ruby objects with attributes that require data type coercions.
Installation
gem i virtus
Basic Usage
require 'virtus'
class User
include Virtus
attribute :name, String
attribute :age, Integer
attribute :birthday, DateTime
end
# setting attributes in the constructor
user = User.new(:name => 'Piotr', :age => 28)
# attribute readers
user.name # => "Piotr"
# hash of attributes
user.attributes # => { :name => "Piotr" }
# automatic coercion
user.age = '28'
user.age # => 28
user.birthday = 'November 18th, 1983'
user.birthday # => #<DateTime: 1983-11-18T00:00:00+00:00 (4891313/2,0/1,2299161)>
Default values
require 'virtus'
class Page
include Virtus
attribute :title, String
attribute :slug, String, :default => lambda { |post, attribute| post.title.downcase.gsub(' ', '-') }
attribute :view_count, Integer, :default => 0
end
page = Page.new(:title => 'Virtus Is Awesome')
page.slug # => 'virtus-is-awesome'
page.view_count # => 0
Coercions
Virtus comes with a builtin coercion library. It's super easy to add your own coercion classes. Take a look:
require 'virtus'
require 'digest/md5'
class MD5 < Virtus::Attribute::Object
primitive String
coercion_method :to_md5
end
module Virtus
class Coercion
class String < Virtus::Coercion::Object
def self.to_md5(value)
Digest::MD5.hexdigest(value)
end
end
end
end
class User
include Virtus
attribute :name, String
attribute :password, MD5
end
user = User.new(:name => 'Piotr', :password => 'foobar')
user.name # => 'Piotr'
user.password # => '3858f62230ac3c915f300c664312c63f'
Custom Attributes
require 'virtus'
require 'json'
module MyApp
module Attributes
class JSON < Virtus::Attribute::Object
primitive Hash
def coerce(value)
::JSON.parse(value)
end
end
end
class User
include Virtus
attribute :info, Attributes::JSON
end
end
user = MyApp::User.new
user.info = '{"email":"[email protected]"}'
user.info # => {"email"=>"[email protected]"}
Contributors
Note on Patches/Pull Requests
- Fork the project.
- Make your feature addition or bug fix.
- Add tests for it. This is important so I don't break it in a future version unintentionally.
- Commit, do not mess with rakefile, version, or history. (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)
- Send me a pull request. Bonus points for topic branches.
Copyright
Copyright (c) 2011 Piotr Solnica. See LICENSE for details.