ActiveEnum¶ ↑

Define enum classes in Rails and use them to enumerate ActiveRecord attributes. Brings together some ideas of similar plugins that I liked and does it they way I prefer.

Enum values are stored in memory at the moment but I plan to add database and yaml.

Install¶ ↑

On Gemcutter:

sudo gem install active_enum

And add to your Rails environment.rb

config.gem 'active_enum'

Example¶ ↑

Define an enum class with values

class Sex < ActiveEnum::Base
  value :id => 1, :name => 'Male'
  value :id => 2, :name => 'Female'
end

Define with id as the key

class Sex < ActiveEnum::Base
  value 1 => 'Male'
  value 2 => 'Female'
end

Define using implicit id values

class Sex < ActiveEnum::Base
  value :name => 'Male'
  value :name => 'Female'
end

Beware that if you change the order of values defined in an enum which don’t have explicit ids, then the ids will change. This could corrupt your data if the enum values have been stored in a model record, as they will no longer map to the original enum.

Enum class usage

Sex[1]        # => 'Male'
Sex['Male']   # => 1
Sex[:male]    # => 1
Sex.to_select # => [['Male', 1], ['Female',2]] for select form helpers

Ordering¶ ↑

To define the sorting of returned values use the order method. Which is useful for to_select method.

class Sex < ActiveEnum::Base
  order :asc

  value :id => 1, :name => 'Male'
  value :id => 2, :name => 'Female'
end

By default the order is ascending (:asc) but you can also choose descending (:desc) or in order of definition (:as_defined). The last option is useful when supplying id values but have a specific order needed to display them.

Enumerate model attributes¶ ↑

Use the enum to enumerate an ActiveRecord model attribute

class User < ActiveRecord::Base
  enumerate :sex, :with => Sex
end

Skip the with option if the enum can be implied from the attribute

class User < ActiveRecord::Base
  enumerate :sex
end

Define enum class implicitly from enumerate block. Enum class is namespaced by model class.

class User < ActiveRecord::Base

  # defines User::Sex
  enumerate :sex do
    value :name => 'Male'
  end
end

Multiple attributes with same enum

class Patient < ActiveRecord::Base
  enumerate :to, :from, :with => Sex
end

Attribute value lookup¶ ↑

Access the enum values and the enum class using the attribute method with a symbol for the enum component you want

user = User.new
user.sex = 1
user.sex         # => 1

user.sex(:id)    # => 1
user.sex(:name)  # => 'Male'
user.sex(:enum)  # => Sex

You can set the default to return the enum name value for enumerated attribute

ActiveEnum.use_name_as_value = true
user.sex # => 'Male'

Boolean check¶ ↑

You can check if the attribute value matches a particular enum value by passing the enum value as an argument to the question method

user.sex?(:male)    # => true
user.sex?(:Male)    # => true
user.sex?('Male')   # => true
user.sex?('Female') # => false

Enum lookup¶ ↑

A convenience method on the class is available to the enum class of any enumerated attribute

User.enum_for(:sex) # => Sex

Bulk definition¶ ↑

Define enum classes in bulk without class files, in an initializer file for example.

ActiveEnum.define do

  # defines Sex
  enum(:sex) do
    value :name => 'Male'
    value :name => 'Female'
  end

  # defines Language
  enum(:language) do
    value :name => 'English'
    value :name => 'German'
  end

end

All defined enum classes are stored in ActiveEnum.enum_classes array if you need look them up or iterate over them.

Model as enum or acts_as_enum¶ ↑

You can make an existing model class behave like an enum class with acts_as_enum

class User < ActiveRecord::Base
  acts_as_enum :name_column => 'first_name'
end

Giving you the familiar enum methods

User[1]
User['Dave']
User.to_select

Formtastic¶ ↑

If you are a formtastic user you can use the extension for an enum input.

In an initialiser:

require 'active_enum/formtastic'

Then in a form you can use the :enum type for attribute inputs which are enumerated.

<% semantic_form_for(@person) do |f| %>
  <%= f.input :sex, :as => :enum %>
<% end %>

This will output a select with the option values taken from the enum class for the attribute.

TODO¶ ↑

• more docs

• storage options of memory, database or yaml

• use custom method name for the enumerated attribute

• named_scopes

• question methods for enum names e.g. user.male?

Copyright © 2009 Adam Meehan, released under the MIT license