module ActionDispatch::Routing::Mapper::Base

:action will be available to the action as part of params.
action within that controller. Anything other than :controller or
controller in your application, and :action maps to the name of an
Two of these symbols are special: :controller maps to the name of a

match ':controller/:action/:id/:user_id'

Rails maps to parts of an incoming HTTP request.
When you set up a regular route, you supply a series of symbols that

def match(path, options=nil)
  mapping = Mapping.new(@set, @scope, path, options || {}).to_route
  @set.add_route(*mapping)
  self
end