Question

I need to implement a custom error page in my rails application that allows me to use erb.

I’ve been following this tutorial (http://blog.tommilewski.net/2009/05/custom-error-pages-in-rails/) and I cannot get it to work locally (or remotely). I am running Rails 2.3.5

Here’s the gist of the approach.

1) in the ‘application_controller’, I over ride the “render_optional_error_file(status_code)” method, and set the visibility to “protected”, like this.

protected

def render_optional_error_file(status_code)
  known_codes = ["404", "422", "500"]
  status = interpret_status(status_code)

  if known_codes.include?(status_code)
    render :template => "/errors/#{status[0,3]}.html.erb", :status => status, :layout => 'errors.html.erb'
  else
    render :template => "/errors/unknown.html.erb", :status => status, :layout => 'errors.html.erb'
  end
end

def local_request?
  true
end

I also created a folder within views called errors and created the following views: 404.html.erb, 422.html.erb, 500.html.erb,unknown.html.erb and I created a new layout “errors.html.erb”

I can’t seem to get it to work. I’ve been trying to trigger the 404 page by navigating to http://localhost:3000/foobar — but, instead of getting the new 404.html.erb, I seem to be getting the standard apache 500 error. This happens when I try both mongrel_rails start and mongrel_rails start -e production.

Answer 1

I would suggest using exceptions to render such error pages, so you can use inheritance to group your error messages…

First, declare some (I usually do it in application_controller.rb)

class Error404 < StandardError; end
class PostNotFound < Error404; end

Then add code to ApplicationController to handle them

class ApplicationController < ActionController::Base

  # ActionController::RoutingError works in Rails 2.x only.
  # rescue_from ActionController::RoutingError, :with => :render_404
  rescue_from Error404, :with => :render_404
  rescue_from PostNotFound, :with => :render_post_not_found


  def render_404
    respond_to do |type| 
      type.html { render :template => "errors/error_404", :status => 404, :layout => 'error' } 
      type.all  { render :nothing => true, :status => 404 } 
    end
    true
  end

  def render_post_not_found
    respond_to do |type| 
      type.html { render :template => "errors/shop_not_found", :status => 404, :layout => 'error' } 
      type.all  { render :nothing => true, :status => 404 } 
    end
    true
  end
end

This renders errors/error_404 with the errors layout. Should get you started 🙂

And in your target_controller:

raise PostNotFound unless @post

---

Edit

Note for Rails 3

for a longer explanation on why ActionController::RoutingError doesn’t work for rails 3:
Rails 3.0 Exception Handling.

Rails ticket 4444

“If your application relies on engines that extend your app with their
own routes, things will break because those routes will never get
fired!”