MagicEnum is a simple ActiveRecord gem that makes it easier to maintain ENUM-like attributes in your models.

Examples:

STATUSES = {
  :draft     => 0,
  :published => 1,
  :approved  => 2,
}
define_enum :status

Before version 1.0.0, the hash with ENUM values was camel-cased. We decided to change it to more rubyish upper-cased constant names. If you're upgrading from pre-1.0.0, please change you constants accordingly. Examples:

Statuses => STATUSES
SimpleStatuses => SIMPLE_STATUSES

Name of inverted hash was changed as well:

StatusesInverted => STATUSES_INVERTED
SimpleStatusesInverted => SIMPLE_STATUSES_INVERTED

Add the "magic_enum" gem to your Gemfile.

gem "magic_enum"

And run bundle install command.

Before using define_enum, you should define constant with ENUM options. Constant name would be pluralized enum attribute name (e.g. SIMPLE_STATUSES simple_status enum). Additional constant named like YOUR_ENUM_INVERTED would be created automatically and would contain inverted hash.

Please note: nil and 0 are not the same values!

You could specify additional options:

• :default — value which will be used when current state of ENUM attribute is invalid or wrong value received. If it has not been specified, min value of the ENUM would be used. Could be specified as a symbol;
• :raise_on_invalid — if true an exception would be raised on invalid enum value received. If it is false, default value would be used instead of wrong one;
• :simple_accessors — if true, additional methods for each ENUM value would be defined in form value?. Methods returns true when ENUM attribute has corresponding value;
• :enum — string with name of the ENUM hash;
• :named_scopes — whether to generate named scopes for values of ENUM (pluralized key names). In addition to per-key named scope, of_name scope will be generated, which accepts a symbol corresponding to ENUM value.

Look the following example:

STATUSES = {
  :unknown   => 0,
  :draft     => 1,
  :published => 2,
  :approved  => 3,
}
define_enum :status, :default => 1, :raise_on_invalid => true, :simple_accessors => true

This example is identical to:

STATUSES = {
  :unknown   => 0,
  :draft     => 1,
  :published => 2,
  :approved  => 3,
}
STATUSES_INVERTED = STATUSES.invert

def self.status_value(status)
  STATUSES[status]
end

def self.status_by_value(value)
  STATUSES_INVERTED[value]
end

def status
  self.class.status_by_value(self[:status]) || self.class.status_by_value(1)
end

def status=(value)
  raise ArgumentError, "Invalid value \"#{value}\" for :status attribute of the #{self.class} model" unless STATUSES.key?(value)
  self[:status] = STATUSES[value]
end

def unknown?
  status == :unknown
end

def draft?
  status == :draft
end

def published?
  status == :published
end

def approved?
  status == :approved
end

This plugin was originally developed for BestTechVideos project by Dmytro Shteflyuk and later cleaned up in Scribd repository and released to the public by Oleksiy Kovyrin. All the code in this package is released under the MIT license. For more details, see the LICENSE file.