Creating routes with an optional path prefix

OK, I've managed to sort out this problem:

THere is no way of doing this in Rails by default (at least, not yet). Instead of using namespaces and default values, I needed to install Sven Fuchs' routing filter.

Once the plugin is installed, I added the following file to my lib directory:

require 'routing_filter/base'module RoutingFilter  class Locale < Base    # remove the locale from the beginning of the path, pass the path    # to the given block and set it to the resulting params hash    def around_recognize(path, env, &block)      locale = nil      path.sub! %r(^/([a-zA-Z]{2})(?=/|$)) do locale = $1; '' end      returning yield do |params|        params[:locale] = locale || 'en'      end    end    def around_generate(*args, &block)      locale = args.extract_options!.delete(:locale) || 'en'      returning yield do |result|        if locale != 'en'          result.sub!(%r(^(http.?://[^/]*)?(.*))){ "#{$1}/#{locale}#{$2}" }        end       end    end  endend

I added this line to routes.rb:

map.filter 'locale'

This basically fills out a before and after hook, generated by the plugin, that wraps the rails routing.

When a url is recognised, and before Rails gets to do anything with it, the around_recognize method is called. This will extract a two-letter code representing the locale, and pass it through in the params, defaulting to 'en' if no locale is specified.

Likewise, when a url is generated, the locale parameter will be pushed into the URL on the left side.

This gives me the following urls and mappings:

/   => :locale => 'en'/en => :locale => 'en'/fr => :locale => 'fr'

All existing url helpers work as before, with the only difference being that unless the locale is specified, it is preserved:

home_path                  => /home_path(:locale => 'en') => /home_path(:locale => 'fr') => /fr

You can define defaults in a route using the :defaults key. Try this:

map.connect ':lang/posts/:id', :controller => 'posts', :action => 'show',                               :defaults => { :lang => 'en' }

I understand that this old question, but it may be useful.

  map.with_options(:path_prefix => ":locale") do |m|    m.resources :posts    m.resources :stories          end

And you have to add before filter to application controller to define locale, such as

before_filter :define_localedef define_locale  if params[:locale] == nil    I18n.locale = 'en'  else    I18n.locale = params[:locale]  endend