Question

I’m using Rails built in I18n (Simple backend). I’ve set the default locale to :en and enabled fallbacks. Let’s say I have translations for a specific item in English and Spanish. Now a German visitor comes to my site and it falls back to English. How would I go about detecting that fallback and wrapping it in a span?

<span class="fallback">Hello</span> instead of just Hello

This way I could then use client side machine translations.

I’m hoping to avoid writing my own backend to replace “Simple”.

Answer 1

Had to resort to over-riding the translate function in I18n::Backend::FallBacks
https://github.com/svenfuchs/i18n/blob/master/lib/i18n/backend/fallbacks.rb

module I18n
  module Backend
    module Fallbacks
      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)
            if locale != fallback
              return "<span class=\"translation_fallback\">#{result}</span>".html_safe unless result.nil?
            else
              return result unless result.nil?
            end
          end
        end
        options.delete(:fallback)

        return super(locale, nil, options.merge(:default => default)) if default
        throw(:exception, I18n::MissingTranslation.new(locale, key, options))
      end
    end
  end
end

I just put this code in an initializer.

It feels very messy to me… I would still love to mark someone else’s better answer as correct.