Question

How can I go about making my routes recognise an optional prefix parameter as follows:

/*lang/controller/id 

In that the lang part is optional, and has a default value if it’s not specified in the URL:

/en/posts/1   => lang = en /fr/posts/1   => lang = fr /posts/1      => lang = en 

EDIT

Ideally, I’m looking to do this across many controllers and actions by mapping a namespace:

map.namespace '*lang' do |lang|   lang.resources :posts   lang.resources :stories end 

Answer 1

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    end end 

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