ruby_rails_404_handling

application_controller.rb

  ...
  include ErrorsHelper
  rescue_from ActionController::RoutingError, ActionController::UnknownController, ::AbstractController::ActionNotFound, ActiveRecord::RecordNotFound, with: lambda { |exception| render_error 404, exception }
  ...

ErrorsController.rb

class ErrorsController < ApplicationController
  def not_found
  end
end

ErrorsHelper.rb

module ErrorsHelper
  def render_error(status_code, exception)
    render :template => "errors/not_found", :status => 404, :layout => "application"
    true  # so we can do "render_404 and return"
  end
end

not_found.html.haml

#message
  Sorry. The page you are looking for cannot be found. 

routes.rb

  match '*rest', :to => 'errors#not_found'