Playing with the Rails Router in isolation

router.rb

class Route
  def initialize(route)
    @route = route
  end

  def to_s
    string =  ""
    string << "#{verb} request to #{path} will dispatch to the class #{controller.camelize}, and call the method #{action}.\n"
    string << "#{controller.camelize} is expected to be defined in #{controller_file}\n"
    string << "There are #{helper_methods.length} helper methods you can call in the controller and the view: #{helper_methods}\n" if helper_methods.any?
    string
  end
  
  def to_h
    { verb: verb, path: path, controller: controller.camelize, action: action, controller_file: controller_file, helper_methods: helper_methods }
  end

  def inspect
    "#<Route #{name} #{verb} #{path} to #{controller}##{action}>"
  end

  def controller_file
    "app/controllers/#{controller}.rb"
  end

  def controller
    "#{@route.defaults[:controller]}_controller"
  end

  def action
    @route.defaults[:action]
  end

  def verb
    @route.verb.source[1...-1] # verb is a regexp like /^GET$/
  end

  def path
    @route.path.ast.to_s
  end

  def url(host="http://example.com")
    File.join(host, path)
  end

  def name
    @route.name
  end

  def helper_methods
    return [] unless name
    [path_helper, url_helper]
  end

  def path_helper
    name && "#{name}_path"
  end

  def url_helper
    name && "#{name}_url"
  end
end

require 'action_dispatch/routing'
route_set = ::ActionDispatch::Routing::RouteSet.new
route_set.draw do
  root 'site#index'
  resources :ducks, only: [:index, :show] do
    member { get :pond }
  end
end

routes = route_set.routes.map { |route| Route.new route }

# =====  Rake Routes output  =====
require 'action_dispatch/routing/inspector'
Rails ||= Class.new { def self.method_missing(*) self end } # hack to get around router coupling
ActionDispatch::Routing::RoutesInspector.new(route_set.routes).format(ActionDispatch::Routing::ConsoleFormatter.new).lines
# => ["   Prefix Verb URI Pattern               Controller#Action\n",
#     "     root GET  /                         site#index\n",
#     "pond_duck GET  /ducks/:id/pond(.:format) ducks#pond\n",
#     "    ducks GET  /ducks(.:format)          ducks#index\n",
#     "     duck GET  /ducks/:id(.:format)      ducks#show"]


# =====  Path Helpers  =====
path_routes  = routes.select { |r| r.path_helper }
helper_width = path_routes.flat_map { |r| r.path_helper }.map(&:length).max
path_routes.map { |r| "%-#{helper_width}s  |  %s" % [r.path_helper, r.path] }
# => ["root_path       |  /",
#     "pond_duck_path  |  /ducks/:id/pond(.:format)",
#     "ducks_path      |  /ducks(.:format)",
#     "duck_path       |  /ducks/:id(.:format)"]


# =====  Url Helpers  =====
url_routes   = routes.select { |r| r.url_helper }
helper_width = url_routes.flat_map { |r| r.path_helper }.map(&:length).max
url_routes.map { |r| "%-#{helper_width}s  |  %s" % [r.url_helper, r.url] }
# => ["root_url        |  http://example.com/",
#     "pond_duck_url   |  http://example.com/ducks/:id/pond(.:format)",
#     "ducks_url       |  http://example.com/ducks(.:format)",
#     "duck_url        |  http://example.com/ducks/:id(.:format)"]


# =====  Explanation  =====
puts routes.join("\n")

# >> GET request to / will dispatch to the class SiteController, and call the method index.
# >> SiteController is expected to be defined in app/controllers/site_controller.rb
# >> There are 2 helper methods you can call in the controller and the view: ["root_path", "root_url"]
# >> 
# >> GET request to /ducks/:id/pond(.:format) will dispatch to the class DucksController, and call the method pond.
# >> DucksController is expected to be defined in app/controllers/ducks_controller.rb
# >> There are 2 helper methods you can call in the controller and the view: ["pond_duck_path", "pond_duck_url"]
# >> 
# >> GET request to /ducks(.:format) will dispatch to the class DucksController, and call the method index.
# >> DucksController is expected to be defined in app/controllers/ducks_controller.rb
# >> There are 2 helper methods you can call in the controller and the view: ["ducks_path", "ducks_url"]
# >> 
# >> GET request to /ducks/:id(.:format) will dispatch to the class DucksController, and call the method show.
# >> DucksController is expected to be defined in app/controllers/ducks_controller.rb
# >> There are 2 helper methods you can call in the controller and the view: ["duck_path", "duck_url"]