EnumAccessor - Simple enum fields for ActiveRecord

EnumAccessor lets you define enum for attributes, and store them as integer in the database.

It is very similar to Official Rails 4.1 Implementation, but EnumAccessor offers quite a few advantages, with even fewer lines of code. :) Compare rails version with enum_accessor.

No-conflict safe predicate methods (user.status_active? instead of user.active?)
Validation
Scope
Translation
Forms

Compatible with ActiveRecord 3 or later.

If you want to handle multiple flags (bit array) with a single integer column, take a look at ActiveFlag.

Usage

Add this line to your application's Gemfile.

gem 'enum_accessor'

Define enum_accessor in a model class.

class User < ActiveRecord::Base
  enum_accessor :gender, [:female, :male]
end

And now you have a set of methods and constants.

user = User.new
user.gender = 'female'  # Takes String or Symbol
user.gender             # => "female"
user.gender_female?     # => true
user.gender_raw         # => 0

user.gender = :male
user.gender_female?     # => false
user.gender_raw         # => 1

user.gender_male!
user.gender_male?       # => true

User.genders            # => { 'female' => 0, 'male' => 1 }

Notice that zero-based numbering is used as database values.

Your migration should look like this.

create_table :users do |t|
  t.integer :gender, default: 0
end

Optionally, it would be a good idea to add limit: 1 on the column for even better space efficiency when the enum set is small.

Manual coding

There are times when it makes more sense to manually pick particular integer values for the mapping.

In such cases, just pass a hash with coded integer values.

enum_accessor :status, ok: 200, not_found: 404, internal_server_error: 500

Scoping query

For querying purpose, use User.genders method to retrieve internal integer values.

User.where_gender(:female)

Also takes multiple values.

User.where_status(:active, :pending)

To use under direct where context (e.g. find_by or find_or_create_by), pass integer value.

Social.find_or_create_by(kind: Social.kinds[:facebook], external_id: facebook_user_id)

Validations

By default, models are validated using inclusion. To disable, pass false to validates option.

enum_accessor :status, [:on, :off], validates: false

You can also pass validation options.

enum_accessor :status, [:on, :off], validates: { allow_nil: true }

Translation

EnumAccessor supports i18n just as ActiveModel does.

For instance, create a Japanese translation in config/locales/ja.yml

ja:
  enum_accessor:
    gender:
      female: 女
      male: 男

and now human_* methods return a translated string. It defaults to humanize method nicely as well.

I18n.locale = :ja
user.human_gender         # => '女'
User.human_genders        # => { 'female' => '女', 'male' => '男' }

I18n.locale = :en
user.human_gender         # => 'Female'
User.human_genders        # => { 'female' => 'Female', 'male' => 'Male' }

Forms

Thanks to the translation support, forms just work as you expect. Pass an inverted human_* hash for the select tag options.

= form_for @user do |f|
  = f.select :gender, User.human_genders.invert

Changelog

v2.3: Added gender_female! bang setter
v2.2:
- Added where_gender_not(:female) scope
v2.1:
- Support for uniqueness validation
v2.0:
- Reworked to remove the "dict" methods. Now User.genders.dict is User.genders and User.genders.human_dict is User.human_genders
v1.1:
- Validate by default again.
- Added :class_attribute option to specify class attribute to hold definitions
- Cache translations on the fly
v1.0:
- Drop support for Ruby 1.8
- Now getter method returns a String rather than a Symbol
- Do not validate by default
- Added where_gender(:female) scope
- Removed the _raw= as setter automatically handles both types
- Removed constants (e.g. User::GENDERS) and now use the class attribute to save the definition
v0.3: Add support for find_or_create_by - just pass integer value

kenn/enum_accessor