STATESMAN

http://connpass.com/event/14398/

Transcript

1. STATESMAN
   STATESMAN
   @kbaba1001
   Powered by Rabbit 2.1.6 and COZMIXNG
   

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2. 自己紹介
   馬場(kbaba1001)
   ESM 4 年目
   

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3. 今日の話
   

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4. is 何？
   ステートマシンを作る gem
   

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5. 特徴
   新しい (2013/10/23〜)
   aasm 風 DSL
   状態遷移の履歴をとる仕組みが
   ある
   

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6. 基本的な構成
   State Machine Class
   Model
   Transition Model
   

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7. State Machine Class
   class TaskStateMachine
   include Statesman::Machine
   state :unstarted, initial: true
   state :started
   state :finished
   event :start do
   transition from: :unstarted, to: :started
   end
   event :finish do
   transition from: :started, to: :finished
   end
   end
   

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8. Model
   class Task < ActiveRecord::Base
   include Statesman::Adapters::ActiveRecordQueries
   has_many :task_transitions, inverse_of: :task
   delegate :current_state, :trigger!, :available_events, to: :state_machine
   def state_machine
   @state_machine ||= TaskStateMachine.new(self, transition_class: TaskTransition)
   end
   private
   def self.transition_class; TaskTransition end
   def self.initial_state; :unstarted end
   end
   

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9. Transition Model
   # create_table "task_transitions", force: true do |t|
   # t.string "to_state", null: false
   # t.text "metadata", default: "{}"
   # t.integer "sort_key", null: false
   # t.integer "task_id", null: false
   # t.boolean "most_recent", null: false
   # t.datetime "created_at"
   # t.datetime "updated_at"
   # end
   #
   class TaskTransition < ActiveRecord::Base
   include Statesman::Adapters::ActiveRecordTransition
   belongs_to :task, inverse_of: :task_transitions
   end
   

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10. 使い方
    task = Task.first
    task.current_state # => "unstarted"
    task.trigger!(:start) # => true/exception
    task.current_state # => "started"
    task.available_events # => [:finish, :deliver]
    Task.in_state(:started) # => [#]
    Task.not_in_state(:unstarted) # => [#]
    

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11. 使ってみた際の工夫
    初期状態を Transition Model に
    記録
    current_state を Model に定義
    

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12. 工夫1
    初期状態を Transition Model に記
    録
    

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13. 初期状態の記録
    task = Task.create
    task.current_state # => "unstarted"
    このときの current_state は
    Transition Model に記録されない
    

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14. after_createで作る
    class Task < ActiveRecord::Base
    has_many :task_transitions, inverse_of: :task
    after_create :create_transition!
    private
    def create_transition!
    task_transitions.create!(
    to_state: TaskStateMachine.initial_state,
    sort_key: 0,
    metadata: {}
    )
    end
    end
    

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15. 工夫2
    current_state を Model に定義
    

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16. current_state とは
    Statesman::Machine#current
    _state
    Taskに紐づくTaskTransitionの
    最新一件のstate名を取得する
    

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17. つらみ
    N+1
    in_state, not_in_state が使い
    にくい (v1.2.0で改善された)
    

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18. 対策
    current_state を Model のカラ
    ムとして定義した。
    多くの場合、今の状態名がわか
    れば良かった。
    

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19. コードの改修
    # migration
    add_column :tasks, :current_state, :string
    # Task Model
    enumerize :current_state, in: TaskStateMachine.states, default: TaskStateMachine.initial_state
    scope :in_state, ->(*states) { where(current_state: states) }
    scope :not_in_state, ->(*states) { where.not(current_state: states) }
    # State Machine Class (TaskStateMachine)
    after_transition do |task, transition|
    task.update_column(:current_state, transition.to_state)
    end
    

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20. 良くなった点
    N+1を考えなくて良い
    in_state, not_in_stateのSQLが
    シンプルに
    enumerizeによりI18n対応
    

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21. 感想
    DSL、履歴が便利
    拡張性もある
    でも細かい所が未成熟
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