Enum machine

Enum machine is a library for defining enums and setting state machines for attributes in ActiveRecord models and plain Ruby classes.

You can visualize the state machine with enum_machine-contrib

Why not state_machines/aasm?

The aasm and state_machines gems suggest calling special methods to change the state. In practice, this can lead to errors. In enum_machine, the state is changed by updating the corresponding field, and the validation of the ability to change from one state to another is done in the after_validation callback. This allows the state of a model to be changed consistently with the usual save!. In addition aasm/state_machines add many autogenerated methods to the model class and instances. This makes it much more difficult to search by the project. Pollutes the method's space. Adds a bottleneck in method naming because you have to remember these methods in your code.

Performance comparison (see test/performance.rb)

Gem	Method
enum_machine	order.state.forming?	894921.3 i/s
state_machines	order.forming?	189901.8 i/s - 4.71x slower
aasm	order.forming?	127073.7 i/s - 7.04x slower

enum_machine	order.state.can_closed?	473150.4 i/s
aasm	order.may_to_closed?	24459.1 i/s - 19.34x slower
state_machines	order.can_to_closed?	12136.8 i/s - 38.98x slower

enum_machine	Order::STATE.values	6353820.4 i/s
aasm	Order.aasm(:state).states.map(&:name)	131390.5 i/s - 48.36x slower
state_machines	Order.state_machines[:state].states.map(&:value)	108449.7 i/s - 58.59x slower

enum_machine	order.state = "forming" and order.valid?	13873.4 i/s
state_machines	order.state_event = "to_forming" and order.valid?	6173.6 i/s - 2.25x slower
aasm	order.to_forming	3095.9 i/s - 4.48x slower

Installation

Add to your Gemfile:

gem 'enum_machine'

Usage

Enums

# With ActiveRecord
class Product < ActiveRecord::Base
  enum_machine :color, %w(red green)
end

# Or with plain class
class Product
  include EnumMachine[color: { enum: %w[red green] }]
end

Product::COLOR.values # => ["red", "green"]
Product::COLOR::RED # => "red"
Product::COLOR::RED__GREEN # => ["red", "green"]

product = Product.new
product.color # => nil
product.color = 'red'
product.color.red? # => true

Aliases

class Product < ActiveRecord::Base
  enum_machine :state, %w[created approved published] do
    aliases(
      'forming' => %w[created approved],
    )
end

Product::STATE.forming # => %w[created approved]

product = Product.new(state: 'created')
product.state.forming? # => true

Transitions

class Product < ActiveRecord::Base
  enum_machine :color, %w[red green blue]
  enum_machine :state, %w[created approved cancelled activated] do
    transitions(
      nil                    => 'red',
      'created'              => [nil, 'approved'],
      %w[cancelled approved] => 'activated',
      'activated'            => %w[created cancelled],
    )

    # Will be executed in `before_save` callback
    before_transition 'created' => 'approved' do |product|
      product.color = 'green' if product.color.red?
    end

    # Will be executed in `after_save` callback
    after_transition %w[created] => %w[approved] do |product|
      product.color = 'red'
    end

    after_transition any => 'cancelled' do |product|
      product.cancelled_at = Time.zone.now
    end
  end
end

product = Product.create(state: 'created')
product.state.possible_transitions # => [nil, "approved"]
product.state.can_activated? # => false
product.state.to_activated! # => EnumMachine::Error: transition "created" => "activated" not defined in enum_machine
product.state.to_approved! # => true; equal to `product.update!(state: 'approved')`

I18n

ru.yml

ru:
  enums:
    product:
      color:
        red: Красный
        green: Зеленый

# ActiveRecord
class Product < ActiveRecord::Base
  enum_machine :color, %w(red green)
end

# Plain class
class Product
  # `i18n_scope` option must be explicitly set to use methods below
  include EnumMachine[color: { enum: %w[red green], i18n_scope: 'product' }]
end

Product::COLOR.human_name_for('red') # => 'Красный'
Product::COLOR.values_for_form # => [["Красный", "red"], ["Зеленый", "green"]]

product = Product.new(color: 'red')
product.color.human_name # => 'Красный'

I18n scope can be changed with i18n_scope option:

# For AciveRecord
class Product < ActiveRecord::Base
  enum_machine :color, %w(red green), i18n_scope: 'users.product'
end

# For plain class
class Product
  include EnumMachine[color: { enum: %w[red green], i18n_scope: 'users.product' }]
end