number_to_currency locale converting

For this to work you need to have a locale file at config/locales/fr.yml. You can get it from here: https://github.com/svenfuchs/rails-i18n/blob/master/rails/locale/fr.yml.

The :locale option only declares to Rails what locale you want it to be. Rails does not have all the translations for every language in the project, and so you must include these translation files yourself.

I know this is a bit late. But just wanted to expalin the above answer. Use it as following:

number_to_currency(aNumber, :locale => :fr)

This uses the file config/locales/fr.yml. You can form your own currency format and define it in config/locales/fr.yml. The File will contain the following:

fr:
   number:
     currency:
        format:
          unit: '€'
          delimiter: ','
          separator: '.'
          precision: 2
          format: '%n%u'

unit is the currency Symbol. also you can format the whole string with the format:. More on this Here