1  # encoding: utf-8
   2 
   3  # This module allows you to easily cache all responses from the backend - thus
   4  # speeding up the I18n aspects of your application quite a bit.
   5  #
   6  # To enable caching you can simply include the Cache module to the Simple
   7  # backend - or whatever other backend you are using:
   8  #
   9  #  I18n::Backend::Simple.send(:include, I18n::Backend::Cache)
  10  #
  11  # You will also need to set a cache store implementation that you want to use:
  12  #
  13  #  I18n.cache_store = ActiveSupport::Cache.lookup_store(:memory_store)
  14  #
  15  # You can use any cache implementation you want that provides the same API as
  16  # ActiveSupport::Cache (only the methods #fetch and #write are being used).
  17  #
  18  # The cache_key implementation assumes that you only pass values to
  19  # I18n.translate that return a valid key from #hash (see
  20  # http://www.ruby-doc.org/core/classes/Object.html#M000337).
  21  module I18n
  22    class << self
  23      @@cache_store = nil
  24      @@cache_namespace = nil
  25 
  26      def cache_store
  27        @@cache_store
  28      end
  29 
  30      def cache_store=(store)
  31        @@cache_store = store
  32      end
  33 
  34      def cache_namespace
  35        @@cache_namespace
  36      end
  37 
  38      def cache_namespace=(namespace)
  39        @@cache_namespace = namespace
  40      end
  41 
  42      def perform_caching?
  43        !cache_store.nil?
  44      end
  45    end
  46 
  47    module Backend
  48      # TODO Should the cache be cleared if new translations are stored?
  49      module Cache
  50        def translate(*args)
  51          I18n.perform_caching? ? fetch(*args) { super } : super
  52        end
  53 
  54        protected
  55 
  56          def fetch(*args, &block)
  57            result = I18n.cache_store.fetch(cache_key(*args), &block)
  58            raise result if result.is_a?(Exception)
  59            result = result.dup if result.frozen? rescue result
  60            result
  61          rescue MissingTranslationData => exception
  62            I18n.cache_store.write(cache_key(*args), exception)
  63            raise exception
  64          end
  65 
  66          def cache_key(*args)
  67            # This assumes that only simple, native Ruby values are passed to I18n.translate.
  68            # Also, in Ruby < 1.8.7 {}.hash != {}.hash
  69            # (see http://paulbarry.com/articles/2009/09/14/why-rails-3-will-require-ruby-1-8-7)
  70            # If args.inspect does not work for you for some reason, patches are very welcome :)
  71            hash = RUBY_VERSION >= "1.8.7" ? args.hash : args.inspect
  72            keys = ['i18n', I18n.cache_namespace, hash]
  73            keys.compact.join('-')
  74          end
  75      end
  76    end
  77  en