Catches ActionController::RoutingError in Rails 3
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Catches ActionController::RoutingError which does not work with Rails 3 out of the box. It basically catches the exception on Rack-level and re-raises it on application-level.

This gem is part of Vidibus, an open source toolset for building distributed (video) applications.

Deprecation Warning

It is not advised to use this gem anymore. At least with Rails 3.2 it won't work. Please implement one of the following alternatives instead:

Alternative One

José Valim revealed a "hidden" feature of Rails 3.2 that comes in handy. In Rails 3.2 you're able to define your own app for handling exceptions that happen in the rack stack. Thus you could set your own router to handle that in application.rb:

config.exceptions_app = self.routes

Since your router is now responsible for dealing with all exceptions, you could define a route that handles 404s:

match '/404', :to => 'errors#not_found'

Alternative Two

Another possibility is to add a catch-all route. But don't put it just at the end of routes.rb because that will disable all routes defined by engines that come with gems and such. Instead, append the route in application.rb:

module PutYourApplicationNameHere
  class Application < Rails::Application
    # Catch 404s
    config.after_initialize do |app|
      app.routes.append{match '*path', :to => 'errors#not_found'}

Addressed Problem

Since Rails 3 is based on Rack, catching a 404 error in your Application controller does not work as expected. The underlying problem is discussed here.


Add the dependency to the Gemfile of your application:

gem 'vidibus-routing_error'

Then call bundle install on your console.


With this gem installed, you are able to handle errors like in past versions of Rails:

class ApplicationController < ActionController::Base
  rescue_from ActionController::RoutingError, :with => :rescue_404

  def rescue_404
    # do something
    # IMPORTANT: If you modify this method, you have to restart the server.

Keep in mind that you have to restart your server when changing the rescue-method!

Underlying Mechanics

This gem implants the middleware Vidibus::RoutingError::Rack into your Rails stack right after ActionDispatch::ShowExceptions which returns a 404 response if no matching route was found for the current request.

Vidibus::RoutingError::Rack catches the 404 status and redirects internally to the route '/routing_error' which is provided by this gem.

Through this route the method RoutingErrorController#rescue gets called which then raises an ActionController::RoutingError on application level so you can rescue this error.

Custom controller for error handling

If you want to handle the error in a specific controller, you can also route the path '/routing_error' in routes.rb to it:

match 'routing_error' => 'my_controller#rescue_404'

The failing URI will be available in the environment variable:


Possible Issues

Catch-all Route

If your application has a catch-route in routes.rb, this gem won't work, because routes provided by engines will be added after any existing routes. If you don't need a catch-all route for other purposes than rescuing from routing errors, you can savely remove it.

Class Caching

Depending on the structure of your application, you might get an error in development like this:

TypeError (User can't be referred)

This error is caused by some caching-reloading madness: The middleware implanted by this gem is cached. But in development, your classes usually aren't. Thus some classes may not be available under certain circumstances, e.g. if you are using before filters for user authentication provided by some engine. You should be able to get rid of the error above by turning on class caching. Try it (and restart the server afterwards):

# development.rb
config.cache_classes = true

If the error is gone, you're lucky as I am. But since it is not feasible to cache classes in development, turn off class caching again and explicitly require the class that couldn't be referred. In my case, it's the user class:

# top of development.rb
require 'app/models/user'


© 2010-2012 Andre Pankratz. See LICENSE for details.

Thank you!

The development of this gem was sponsored by Käuferportal: