= 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 (c) 2009 Adam Meehan, released under the MIT license