+# I18n locale fallbacks are useful when you want your application to use
+# translations from other locales when translations for the current locale are
+# missing. E.g. you might want to use :en translations when translations in
+# your applications main locale :de are missing.
+#
+# To enable locale fallbacks you can simply include the Fallbacks module to
+# the Simple backend - or whatever other backend you are using:
+#
+# I18n::Backend::Simple.include(I18n::Backend::Fallbacks)
+module I18n
+ @@fallbacks = nil
+
+ class << self
+ # Returns the current fallbacks implementation. Defaults to +I18n::Locale::Fallbacks+.
+ def fallbacks
+ @@fallbacks ||= I18n::Locale::Fallbacks.new
+ end
+
+ # Sets the current fallbacks implementation. Use this to set a different fallbacks implementation.
+ def fallbacks=(fallbacks)
+ @@fallbacks = fallbacks
+ end
+ end
+
+ module Backend
+ module Fallbacks
+ # Overwrites the Base backend translate method so that it will try each
+ # locale given by I18n.fallbacks for the given locale. E.g. for the
+ # locale :"de-DE" it might try the locales :"de-DE", :de and :en
+ # (depends on the fallbacks implementation) until it finds a result with
+ # the given options. If it does not find any result for any of the
+ # locales it will then throw MissingTranslation as usual.
+ #
+ # The default option takes precedence over fallback locales only when
+ # it's a Symbol. When the default contains a String, Proc or Hash
+ # it is evaluated last after all the fallback locales have been tried.
+ def translate(locale, key, options = {})
+ return super if options[:fallback]
+ default = extract_non_symbol_default!(options) if options[:default]
+
+ options[:fallback] = true
+ I18n.fallbacks[locale].each do |fallback|
+ catch(:exception) do
+ result = super(fallback, key, options)
+ return result unless result.nil?
+ end
+ end
+ options.delete(:fallback)
+
+ return super(locale, nil, options.merge(:default => default)) if default
+ throw(:exception, I18n::MissingTranslation.new(locale, key, options))
+ end
+
+ def extract_non_symbol_default!(options)
+ defaults = [options[:default]].flatten
+ first_non_symbol_default = defaults.detect{|default| !default.is_a?(Symbol)}
+ if first_non_symbol_default
+ options[:default] = defaults[0, defaults.index(first_non_symbol_default)]
+ end
+ return first_non_symbol_default
+ end
+
+ end
+ end
+end