bitmask-attribute

Transparent manipulation of bitmask attributes.

Simply declare an existing integer column as a bitmask with its possible values.

class User < ActiveRecord::Base
  bitmask :roles, :as => [:writer, :publisher, :editor, :proofreader] 
end

You can then modify the column using the declared values without resorting to manual bitmasks.

user = User.create(:name => "Bruce", :roles => [:publisher, :editor])
user.roles
# => [:publisher, :editor]
user.roles << :writer
user.roles
# => [:publisher, :editor, :writer]

It's easy to find out if a record has a given value:

user.roles?(:editor)
# => true

You can check for multiple values (uses an and boolean):

user.roles?(:editor, :publisher)
# => true
user.roles?(:editor, :proofreader)
# => false

Or, just check if any values are present:

user.roles?
# => true

A couple useful named scopes are also generated when you use bitmask:

User.with_roles
# => (all users with roles)
User.with_roles(:editor)
# => (all editors)
User.with_roles(:editor, :writer)
# => (all users who are BOTH editors and writers)

Later we'll support an or boolean; for now, do something like:

User.with_roles(:editor) + User.with_roles(:writer)
# => (all users who are EITHER editors and writers)

Find records without any bitmask set:

User.without_roles
# => (all users without a role)

Later we'll support finding records without a specific bitmask.

You can add your own methods to the bitmasked attributes (similar to named scopes):

bitmask :other_attribute, :as => [:value1, :value2] do
  def worked?
    true
  end
end

user = User.first
user.other_attribute.worked?
# => true

IMPORTANT: Once you have data using a bitmask, don't change the order of the values, remove any values, or insert any new values in the :as array anywhere except at the end. You won't like the results.

Please feel free to fork & contribute fixes via GitHub pull requests. The official repository for this project is http://github.com/bruce/bitmask-attribute

Issues can be reported at http://github.com/bruce/bitmask-attribute/issues

Thanks to the following contributors:

• Jason L Perry
• Nicolas Fouché

Copyright (c) 2007-2009 Bruce Williams. See LICENSE for details.