replacing ActionController::Routing::RouteSet::Mapper.send

Hi there,

I'm following http://edgeguides.rubyonrails.org/plugins.html and at
chapter 8, I'm told to add:
ActionController::Routing::RouteSet::Mapper.send :include,
Yaffle::Routing::MapperExtensions

In order to add the routes of my plugin in my Rails app...

Unfornately, ActionController::Routing is deprecated,

What should I use instead?

Thanks in advance,

Ben