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.
$ gem install virtus
or
# ./Gemfile
gem 'virtus', '0.0.7'
require 'virtus'
class User
include Virtus
attribute :name, String
attribute :age, Integer
attribute :birthday, DateTime
end
user = User.new :name => 'Piotr', :age => 28
user.attributes
# => { :name => "Piotr", :age => 28 }
user.name
# => "Piotr"
user.age = '28'
# => 28
user.age.class
# => Fixnum
user.birthday = 'November 18th, 1983'
# => #<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 :views, Integer, :default => 0
attribute :slug, String, :default => lambda { |page, attribute| page.title.downcase.gsub(' ', '-') }
end
page = Page.new :title => 'Virtus Is Awesome'
page.slug
# => 'virtus-is-awesome'
page.views
# => 0
Adding 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'
# Our new attribute type
class MD5 < Virtus::Attribute::Object
primitive String
coercion_method :to_md5
end
# Defining the Coercion method
module Virtus
class Coercion
class String < Virtus::Coercion::Object
def self.to_md5(value)
Digest::MD5.hexdigest value
end
end
end
end
# And now the user!
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 MyAppClass
# Defining the custom attribute(s)
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":"john@domain.com"}'
# => {"email"=>"john@domain.com"}
user.info.class
# => Hash
- 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 (c) 2011 Piotr Solnica
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.