1  # encoding: utf-8
   2 
   3  module I18n
   4    module Backend
   5      # Backend that chains multiple other backends and checks each of them when
   6      # a translation needs to be looked up. This is useful when you want to use
   7      # standard translations with a Simple backend but store custom application
   8      # translations in a database or other backends.
   9      #
  10      # To use the Chain backend instantiate it and set it to the I18n module.
  11      # You can add chained backends through the initializer or backends
  12      # accessor:
  13      #
  14      #   # preserves the existing Simple backend set to I18n.backend
  15      #   I18n.backend = I18n::Backend::Chain.new(I18n::Backend::ActiveRecord.new, I18n.backend)
  16      #
  17      # The implementation assumes that all backends added to the Chain implement
  18      # a lookup method with the same API as Simple backend does.
  19      class Chain
  20        include Base
  21 
  22        attr_accessor :backends
  23 
  24        def initialize(*backends)
  25          self.backends = backends
  26        end
  27 
  28        def reload!
  29          backends.each { |backend| backend.reload! }
  30        end
  31 
  32        def store_translations(locale, data, options = {})
  33          backends.first.store_translations(locale, data, options = {})
  34        end
  35 
  36        def available_locales
  37          backends.map { |backend| backend.available_locales }.flatten.uniq
  38        end
  39 
  40        def translate(locale, key, options = {})
  41          return key.map { |k| translate(locale, k, options) } if key.is_a?(Array)
  42 
  43          default = options.delete(:default)
  44          namespace = {}
  45          backends.each do |backend|
  46            begin
  47              options.update(:default => default) if default and backend == backends.last
  48              translation = backend.translate(locale, key, options)
  49              if namespace_lookup?(translation, options)
  50                namespace.update(translation)
  51              elsif !translation.nil?
  52                return translation
  53              end
  54            rescue MissingTranslationData
  55            end
  56          end
  57          return namespace unless namespace.empty?
  58          raise(I18n::MissingTranslationData.new(locale, key, options))
  59        end
  60 
  61        def localize(locale, object, format = :default, options = {})
  62          backends.each do |backend|
  63            begin
  64              result = backend.localize(locale, object, format, options) and return result
  65            rescue MissingTranslationData
  66            end
  67          end
  68          raise(I18n::MissingTranslationData.new(locale, format, options))
  69        end
  70 
  71        protected
  72          def namespace_lookup?(result, options)
  73            result.is_a?(Hash) and not options.has_key?(:count)
  74          end
  75      end
  76    end
  77  end