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Ruby On Rails Gemまとめ -state_machine-

Last updated at Posted at 2014-06-12

##state_machineとは
「state_machine」は公開・非公開、ON・OFFなどの属性の状態をよりシンプルに管理できるようにする。

##インストール
Gemfileに以下を追加。

gem "state_machine"

ターミナルで$ bundle installを実行。

##使い方
例として、Article(記事)モデルのカラム「status」に「下書き(draft)、公開(public)、非公開(private)」の3つの状態を保持し、また、「delete_flag」に「on、off」の2つの状態を保持するとします。

まずは、以下のように定義します。

$ rails g model Article status
article.rb
class Article < ActiveRecord::Base
  state_machine :status, initial: :draft do
    state :draft
    state :public
    state :private

    before_transition on: :draft, do: :preview_on  #状態の変更前に実行される
	after_transition draft: :public, do: :set_public_date  #状態の変更後に実行される

    event :change_status do
      transition draft: :public
      transition public: :private
    end
  end

  state_machine :delete_flag, initial: :off do
    state :on, value: 1
    state :off, value: 0

    event :delete_on do
      transition off: :on
    end

    event : delete_off do
      transition on: :off
    end
  end

  def set_public_date
    #公開日の設定、保存の処理
  end

  def preview_on
    #プレビュー機能をactiveに設定する処理
  end
end

使い方は、以下のようになります。

article = Article.new

"・statusの状態を表示"
article.status  # => "draft"(initialで初期がdraft)

"・イベント「change_status」を実行"
article.change_status
article.status  # => "public"(change_statusでdraftからpublicに変更)

"・statusはdraftか?publicか?"
article.draft?  # => false
article.public?  # => true

"・delete_flagの状態、valueを表示"
article.delete_flag_state  # => 0
article.delete_flag_name  # => :off(_nameだとシンボル)

"・イベント「change_status」を実行"
article.delete_on
article.delete_flag  # => "on"
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