Awesome

Sequel Statesman

Ships Sequel adapters and plugins for Statesman

Regular Configuration

Similar to the ActiveRecord configuration but with the changes required for Sequel:

require 'sequel-statesman'

Statesman.configure do
  storage_adapter(Statesman::Adapters::Sequel)
end

class UserStateMachine
  include Statesman::Machine

  state :invited, initial: true
  state :registered

  transition from: :invited, to: :registered
end

class UserTransition < Sequel::Model
  include Statesman::Adapters::SequelTransition

  many_to_one :user
end

class User < Sequel::Model
  include Statesman::Adapters::SequelQueries

  one_to_many :user_transitions

  def state_machine
    @state_machine ||= UserStateMachine.new(self, transition_class: UserTransition)
  end

  def self.transition_class
    UserTransition
  end
  private_class_method :transition_class

  def self.initial_state
    :invited
  end
  private_class_method :initial_state
end

Create your transitions table:

Sequel.migration do
  up do
    create_table(:user_transitions) do
      primary_key :id

      String :to_state, null: false, size: 255
      String :metadata, default: "{}"
      Integer :sort_key, null: false
      TrueClass :most_recent, null: false
      # Remove last argument above if your database does not support
      # partial indexes

      foreign_key :user_id, :users, null: false

      index %i[user_id sort_key], unique: true
      index %i[user_id most_recent], unique: true, where: 'most_recent'
      # Remove last argument above if your database does not support
      # partial indexes
    end
  end

  down do
    drop_table(:user_transitions)
  end
end

JSON Column

If you want to use your database support for json on the metadata column, just don't include SequelTransition on your transition model and also perform the adjusts on the migration.

For Postgres check the pg_json extension.

Sequel Plugin

You will perform the same configuration above, except for the model:

class User < Sequel::Model
  plugin :statesman
end

The following methods will be delegated to the state machine:

• #current_state
• #state_history
• #last_transition

The following methods will be defined on your model:

• .initial_state
• #state_machine
• #state_name? method for each state on your state machine
• #state_name!(metadata={}) method for each state on your state machine.
• #transition_metadata last metadata available
• #merge_transition_metadata(metadata) update last metadata available
• #refresh overriden to also reload your states

Configuration

You may perform individual model configuration when the plugin is included:

plugin :statesman, transition_class: UserEvent,
                   state_machine_class: UserMachine

Or globally:

require 'sequel/plugins/statesman'
Sequel::Plugins::Statesman.configure!({
  transition_class: ->(model) { "#{model.name}Event".constantize }
  state_machine_class: ->(model) { "#{model.name}Machine".constantize }
})

The defaults are:

{
  # Define #state! and #state? methods
  define_state_methods: true,
  # Transitions are automatically destroyed when the parent instance is destroyed
  destroy_transitions: true,
  # Include SequelQueries automatically
  include_queries: true,
  # The transition class for the model
  transition_class: ->(model) { "#{model.name}Transition".constantize },
  # The state machine for the model
  state_machine_class: ->(model) { "#{model.name}StateMachine".constantize }
}

Sequel Timestamps

If your transition classes use the timestamps plugin you may include the statesman_timestamps plugin to add the following DatasetMethods:

• .state_changed_after(date) to filter records after the last transition
• .state_changed_before(date) to filter records before the last transition

You may configure the columns to be used, (default created_at):

plugin :statesman_timestamps, created: :creation_date

# or globally
require 'sequel/plugins/statesman_timestamps'
Sequel::Plugins::StatesmanTimestamps.configure! created: :creation_date

Credit

This gem was born from this PR from @appleton. Thanks!

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/badosu/statesman-sequel

License

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