ステートマシーンのRuby実装 ほぼ AASMと同じ使い方。

gistfile1.rb

module StateMachine
  class Event
    def transition opt={from:nil,to:nil,guard:nil}
      self.ts ||= {}
      self.ts[ opt[:from] ] = opt if (opt[:from].is_a? String) || (opt[:from].is_a? Symbol)
      opt[:from].each do |name|
        ts[name] = opt
      end if opt[:from].is_a? Array
    end
    attr_accessor :ts
  end
  class Smg
    def initialize name,klass
      self.name = name
      self.klass = klass
      self.states = {}
      smg = self
      klass.class_eval do 
        define_method :initialize do |*args|
          super(*args)
          smg.states.each do |n,s|
            next unless s[:initial]
            send s[:enter] if s[:enter]
            send "#{name}=",n
          end
        end
      end
    end
    def state name, opt={enter:nil, initial:nil}
      self.states[ name ] = opt
    end
    def event name, opt={before:nil,after:nil}, &block
      smg = self
      event = Event.new
      event.instance_eval &block
      klass.class_eval do
        define_method name do
          transition = event.ts[ send(smg.name) ]
          return unless transition
          return if transition[:guard] && send(transition[:guard])
          raise "not state #{transition[:to]}" unless state = smg.states[ transition[:to] ]
          send opt[:before] if opt[:before]
          send state[:enter] if state[:enter]
          send "#{smg.name}=", transition[:to]
          send opt[:after] if opt[:after]
          send :save
        end
      end
    end
    attr_accessor :name
    attr_accessor :klass
    attr_accessor :states
    attr_accessor :instance
  end

  def self.included(klass)
    klass.class.instance_eval do
      define_method :smg do |name,&block|
        _smg = Smg.new name,klass
        _smg.instance_eval &block
      end
    end
  end
end