1  # encoding: utf-8
   2 
   3  # I18n locale fallbacks are useful when you want your application to use
   4  # translations from other locales when translations for the current locale are
   5  # missing. E.g. you might want to use :en translations when translations in
   6  # your applications main locale :de are missing.
   7  #
   8  # To enable locale fallbacks you can simply include the Fallbacks module to
   9  # the Simple backend - or whatever other backend you are using:
  10  #
  11  #   I18n::Backend::Simple.send(:include, I18n::Backend::Fallbacks)
  12  module I18n
  13    @@fallbacks = nil
  14 
  15    class << self
  16      # Returns the current fallbacks implementation. Defaults to +I18n::Locale::Fallbacks+.
  17      def fallbacks
  18        @@fallbacks ||= I18n::Locale::Fallbacks.new
  19      end
  20 
  21      # Sets the current fallbacks implementation. Use this to set a different fallbacks implementation.
  22      def fallbacks=(fallbacks)
  23        @@fallbacks = fallbacks
  24      end
  25    end
  26 
  27    module Backend
  28      module Fallbacks
  29        # Overwrites the Base backend translate method so that it will try each
  30        # locale given by I18n.fallbacks for the given locale. E.g. for the
  31        # locale :"de-DE" it might try the locales :"de-DE", :de and :en
  32        # (depends on the fallbacks implementation) until it finds a result with
  33        # the given options. If it does not find any result for any of the
  34        # locales it will then raise a MissingTranslationData exception as
  35        # usual.
  36        #
  37        # The default option takes precedence over fallback locales
  38        # only when it's not a String. When default contains String it
  39        # is evaluated after fallback locales.
  40        def translate(locale, key, options = {})
  41          default = extract_string_default!(options) if options[:default]
  42 
  43          I18n.fallbacks[locale].each do |fallback|
  44            begin
  45              result = super(fallback, key, options)
  46              return result unless result.nil?
  47            rescue I18n::MissingTranslationData
  48            end
  49          end
  50 
  51          return super(locale, nil, options.merge(:default => default)) if default
  52          raise(I18n::MissingTranslationData.new(locale, key, options))
  53        end
  54 
  55        def extract_string_default!(options)
  56          defaults = Array(options[:default])
  57          if index = find_first_string_default(defaults)
  58            options[:default] = defaults[0, index]
  59            defaults[index]
  60          end
  61        end
  62 
  63        def find_first_string_default(defaults)
  64          defaults.each_index { |ix| return ix if String === defaults[ix] }
  65          nil
  66        end
  67      end
  68    end
  69  end