request_store_cache.rb

# frozen_string_literal: true

# Cache store that gets automatically expired after each request
#
# @example
#   UsersCache = RequestStore::Cache.new(namespace: 'users')
#   UsersCache.read(:user1)
#   # => nil
#   UsersCache.fetch(:user1) { User.find(1) }
#   # => #<User id:1 ...>
#   UsersCache.read(:user1)
#   # => #<User id:1 ...>
#   UsersCache.write(:user1, User.find(2))
#   # => true
#   UsersCache.delete(:user1)
#   # => true
#
class RequestStore::Cache
  def initialize(namespace:)
    @namespace = namespace
  end

  delegate :clear, to: :data

  def read(key)
    data[key]
  end

  def write(key, value)
    data[key] = value
    true
  end

  def fetch(key)
    if data.key?(key)
      data[key]
    else
      data[key] = yield
    end
  end

  private

  def data
    RequestStore[@namespace] ||= {}
  end
end