h1. classy_enum ClassyEnum is a Ruby on Rails gem that adds class-based enumerator functionality to ActiveRecord attributes. h2. Requirements *Rails:* Any version of Rails 2.3.x or Rails 3.0.x. (Older versions of Rails may work, but have not been tested) *Ruby:* Ruby 1.8.7 and 1.9.2. h2. Installation The gem is hosted at "rubygems.org":https://rubygems.org/gems/classy_enum and can be installed with: @gem install classy_enum@ You will also need to add @app/enums@ as an autoloadable path. This configuration will depend on which version of rails you are using. h2. Example Usage The most common use for ClassyEnum is to replace database lookup tables where the content and behavior is mostly static and has multiple "types". In this example, I have an ActiveRecord model called @Alarm@ with an attribute called @priority@. Priority is stored as a string (VARCHAR) type in the database and is converted to an enum value when requested. h3. 1. Generate the Enum The fastest way to get up and running with ClassyEnum is to use the built-in Rails generator like so: Rails 2.3.x:

script/generate classy_enum Priority low medium high

Rails 3.x

rails g classy_enum Priority low medium high

A new enum template file will be created at app/enums/priority.rb that will look like:

class Priority < ClassyEnum::Base
  enum_classes :low, :medium, :high
end

class PriorityLow < Priority
end

class PriorityMedium < Priority
end

class PriorityHigh < Priority
end

The @enum_classes@ macro will add all the ClassyEnum behavior, which is described further down in this document. h3. 2. Customize the Enum The generator creates a default setup, but each enum member can be changed to fit your needs. Using the @enum_classes@ method, I have defined three priority levels: low, medium, and high. Each priority level can have different properties and methods associated with it. I would like to add a method called @send_email?@ that all member subclasses respond to. By default this method will return false, but will be overridden for high priority alarms to return true.

class Priority < ClassyEnum::Base
  enum_classes :low, :medium, :high

  def send_email?
    false
  end
end

class PriorityHigh < Priority
  def send_email?
    true
  end
end

Note: Defining the subclasses within your enum file is only required when you will be overriding behavior and/or properties. The member subclasses still exist without being defined here because ClassyEnum.enum_classes automatically creates a class for each member. The generator only creates these subclass definitions for convenience, but they can be deleted as shown in this example. h3. 3. Setup the ActiveRecord model My ActiveRecord Alarm model needs a text field that will store a string representing the enum member. An example model schema might look something like:

create_table "alarms", :force => true do |t|
  t.string   "priority"
end

Then in my model I've added a line that calls @classy_enum_attr@ with a single argument representing the enum I want to associate with my model. I am also delegating the send_email? method to my Priority enum class.

class Alarm < ActiveRecord::Base
  classy_enum_attr :priority

  delegate :send_email?, :to => :priority
end

With this setup, I can now do the following:

@alarm = Alarm.create(:priority => :medium)

@alarm.priority  # => PriorityMedium
@alarm.priority.is? :medium # => true
@alarm.priority.to_s # => 'medium'
@alarm.priority.name # => 'Medium'

# Should this alarm send an email?
@alarm.send_email? # => false
@alarm.priority = :high
@alarm.send_email? # => true

The enum field works like any other model attribute. It can be mass-assigned using @update_attribute(s)@. h2. Special Cases What if your enum class name is not the same as your model's attribute name? No problem! Just use a second arugment in @classy_enum_attr@ to declare the attribute name. In this case, the model's attribute is called *alarm_priority*.

class Alarm < ActiveRecord::Base
  classy_enum_attr :alarm_priority, :enum => :priority
end

@alarm = Alarm.create(:alarm_priority => :medium)
@alarm.alarm_priority  # => PriorityMedium

h2. Model Validation An ActiveRecord validator @validates_inclusion_of :field, :in => ENUM.all, :allow_nil => true@ is automatically added to your model when you use @classy_enum_attr@. If your enum only has members low, mediume, and high, then the following validation behavior would be expected:

@alarm = Alarm.new(:priority => :really_high)
@alarm.valid? # => false
@alarm.priority = :high
@alarm.valid? # => true

h2. Working with ClassyEnum outside of ActiveRecord While ClassyEnum was designed to be used directly with ActiveRecord, it can also be used outside of it. Here are some examples based on the enum class defined earlier in this document. Instantiate an enum member subclass *PriorityLow*

# These statements are all equivalent
low = Priority.build(:low)
low = Priority.build('low)
low = Priority.find(:low)
low = PriorityLow.new

Get a list of the valid enum options

Priority.valid_options # => low, mediume, high

h2. Formtastic Support To add ClassyEnum support to Formtastic, add the following to your formtastic.rb initializer (config/initializers/formtastic.rb):

Formtastic::SemanticFormHelper.builder = ClassyEnum::SemanticFormBuilder