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 transitions map with enum_machine-contrib

Why is enum_machine better then state_machines / aasm?

• faster 5x
• code lines: enum_machine - 348, AASM - 2139
• namespaced (via attr) by default: order.state.to_collected
• aliases
• guarantees of existing transitions
• simple run transitions with callbacks order.update(state: "collected") or order.state.to_collected
• aasm / state_machines event driven, enum_machine state driven

# aasm
event :complete do # complete/collected - dichotomy between states and events
  before { puts "event complete" }
  transitions from: :collecting, to: :collected
end

# pay/archived difficult to remember the relationship between statuses and events
# try to explain this to the logic of business stakeholders
event :pay do
  transitions from: [:created, :collected], to: :archived
end

order = Order.create(state: "collecting")
order.update(state: "archived") # not check transitions, invalid logic
order.update(state: "collected") # not run callbacks 
order.complete # need use event for transition, but your object in UI and DB have only states

# enum_machine
transitions( # simple readable transitions map
  "collecting" => "collected",
  "collected"  => "archived",
)
before_transition("collecting" => "collected") { puts "event complete" }

order = Order.create(state: "collecting")
order.update(state: "archived") # checked transitions, raise exception
order.update(state: "collected") # run callbacks

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
  # attributes must be defined before including the EnumMachine module
  attr_accessor :color
  
  include EnumMachine[color: { enum: %w[red green] }]
  # or reuse from model
  Product::COLOR.decorator_module
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
product.color.human_name # => "Красный"

Aliases

class Product < ActiveRecord::Base
  enum_machine :state, %w[created approved published] do
    aliases(
      "forming" => %w[created approved],
    )
  end
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(any => any) - allow all transitions
    transitions(
      nil                    => "created",
      "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: "approve")`

Skip transitions

product = Product.new(state: "created")
product.skip_state_transitions { product.save }

method generated as skip_#{enum_name}_transitions

Skip in factories

FactoryBot.define do
  factory :product do
    name { Faker::Commerce.product_name }
    to_create { |product| product.skip_state_transitions { product.save! } }
  end
end

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
  # attributes must be defined before including the EnumMachine module
  attr_accessor :color
  # `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

Benchmarks

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

License

The gem is available as open source under the terms of the MIT License.