Rails/Model(Active Record)のConcern

Ruby on RailsでModelの共通処理を切り出すときに使われるConcernの紹介です。

🐝 Concernの書き方

includeブロックでscope, Callbackなどを定義
module ClassMethodsのブロックにクラス・メソッドを定義
インスタンスメソッドはモジュール直下

module MyConcern
  extend ActiveSupport::Concern

  # Scope や Callback 処理を実装する
  included do
    scope :without_deleted, lambda{ where(deleted_at: nil) }
  end

  module ClassMethods
    def foo
      puts 'foo'
    end
  end

  def bar
    puts 'bar'
  end
end

🐮 Example

ElasticSearch の処理をconcernで分離

module Article::Searchable
  extend ActiveSupport::Concern

  included do
    include Elasticsearch::Model

    # Customize the index name
    index_name "green_application"

    # Set up index configuration and mapping
    settings index: {
      number_of_shards:   1,
      number_of_replicas: 0,
      analysis: {
        analyzer: {
          kuromoji_analyzer: {
            type:      'custom',
            tokenizer: 'kuromoji_tokenizer',
            filter:    ['kuromoji_baseform', 'pos_filter', 'greek_lowercase_filter', 'cjk_width'],
          },
          ngram_analyzer: {
            tokenizer: "ngram_tokenizer"
          }
        }
      }
    } do
      mapping _source: { enabled: true }, 
_all: { enabled: true, analyzer: "kuromoji_analyzer" } do
        indexes :id, type: 'integer', index: 'not_analyzed'
        indexes :title, type: 'string', analyzer: 'kuromoji_analyzer'
         # ...
      end
    end

    def as_indexed_json(options={})
      hash = self.as_json(
        include: {
          job_types: { only: [:job_type_id] },
           # ...
        }
      )
      hash['client_name'] = client.name

      hash
    end
  end

  module ClassMethods
    def create_index!(options={})
      client = __elasticsearch__.client
      client.indices.delete index: "green_application" rescue nil if options[:force]
      client.indices.create index: "green_application",
      body: {
        settings: settings.to_hash,
        mappings: mappings.to_hash
      }
    end
  end
end