Rails7でCacheを利用する（purgeも含む）

環境

• Ruby on Rails 7.0.5
• Ruby 3.2.2

コード例

キャッシュを使う（ない場合は作る）

app/controllers/users_controller.rb

  def users_for_select
    @users = Rails.cache.fetch(User::CACHE_FOR_SELECT, expires_in: 5.minutes) do
      User.active.select(:id, :email, :name)
    end
  end

キャッシュのキー定義とデータ変更時に削除するコード

app/models/user.rb

  class User
    CACHE_FOR_SELECT = 'users_for_select'

    after_commit :purge_cache_for_select, on: %i[create update destroy]

    private

    def purge_cache_for_select
      Rails.cache.delete(CACHE_FOR_SELECT)
    end
  end

キャッシュストアの定義

config/application.rb

config/application.rb

  config.cache_store = :memory_store, { size: 64.megabytes }
  # デフォルトは32MB
  # 本番環境では、Redis等を利用する

config/environments/test.rb

config/environments/test.rb

  config.cache_store = :memory_store, { size: 64.megabytes }
  # これがないと、テストで ActiveSupport::Cache::NullStore error が出る

テストコード

spec/models/tenant_spec.rb

  describe '#purge_cache_for_select' do
    let!(:user) { create(:user) }

    before do
      allow(Rails.cache).to receive(:delete)
    end

    it 'purges cache on create' do
      create(:tenant)
      expect(Rails.cache).to have_received(:delete).with(User::CACHE_FOR_SELECT)
    end

    it 'purges cache on update' do
      tenant.update(name: 'new name')
      expect(Rails.cache).to have_received(:delete).with(User::CACHE_FOR_SELECT)
    end

    it 'purges cache on destroy' do
      tenant.destroy
      expect(Rails.cache).to have_received(:delete).with(User::CACHE_FOR_SELECT)
    end
  end