haz_enum¶ ↑

haz_enum is a ActiveRecord extension to allow associations to enumerations.

Installation¶ ↑

haz_enum is hostet on rubygems.org, so yoou can just do

gem install haz_enum

or if you use bundler, just add the following line to your Gemfile:

gem "haz_enum"

Example with renum¶ ↑

renum is a perfect library for enumerations in ruby (see github.com/duelinmarkers/renum). Here is a simple renum definition:

enum :Roles do
  Admin()
  Supervisor()
  ContentManager()
end

in your AR-model you can now write

class User < ActiveRecord
  has_enum :role
end

what you need is a column in your db named role with type string.

user = User.create(:role => Roles::Admin)
user.has_role?(Roles::Admin) => true
user.has_role?(Roles::Supervisor) => false

The example above realizes one role per user. But what if you want to have multiple Roles per user? Just change has_enum to has_set and rename the column to roles:

class User < ActiveRecord
  has_set :roles
end

user = User.create(:roles => Roles::Admin)
user.has_role?(Roles::Admin) => true
user.has_role?(Roles::Supervisor) => false

or

user = User.create(:roles => [Roles::Admin, Roles::Supervisor])
user.has_role?(Roles::Admin) => true
user.has_role?(Roles::Supervisor) => true

now roles behaves just like an array, so you can also do

user = User.create(:roles => Roles::Admin)
user.roles << Roles::Supervisor
user.has_role?(Roles::Admin) => true
user.has_role?(Roles::Supervisor) => true

Using bitfields¶ ↑

If you have an enum with many possible values you can switch from :yml to field_type :bitfield.

class User < ActiveRecord
  has_set :roles, :field_type => :bitfield
end

Your db-column has to be an integer for field_type bitfield. If you use mysql with int(11) you are able to have up to 64 different values in your enumeration.

You do not need renum¶ ↑

…but it really makes sense to use this library. If you really do not want to use it you have to implement against an interface. Here is a simple ruby module example to get the same results as above for has_enum:

module Roles
  class Admin; def self.name; "Admin"; end; end
  class Supervisor; def self.name; "Supervisor"; end; end
  class ContentManager; def self.name; "ContentManager"; end; end
end

You cannot use this for has_set and field_type :yml since you cannot dump anonymous classes. But you can use field_type :bitfield. Then your class could look something like that:

module Roles
  class Admin
    def self.bitfield_index; 1; end
  end
  class Supervisor
    def self.bitfield_index; 2; end
  end
  class ContentManager
    def self.bitfield_index; 3; end
  end
  class <<self
    def values
      Roles.constants.collect { |c| Roles.const_get(c) }
    end
  end
end

As you can see, your classes have to respond to bitfield_index and your wrapping module has to respond to values and return all available classes. So now you could do:

class User < ActiveRecord
  has_enum :role, :field_type => :bitfield
end

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 © 2010 Galaxy Cats IT Consulting GmbH. See LICENSE for details.