#53 Handling Exceptions

Thanks, very good cast like all before. Will you make one about authorization and authentication?

Hello Ryan, you're making a terrific work over railscasts and the rails community, haha, is getting difficult to follow u in each episode (time!! you know! :()... cheers from Santiago de Chile.

I'm a little bit disappointed about this episode. I found it useful to know about such methods, but it wasn't what i expected! in fact, I thought that it will be sth like try.. catch.. in other languages to keep the users in the default layout.

Oh! i clicked in @Nico Orellana to visit the website.. but it seems that users are not very pleased to add each time the http:// :)

Thanks for a great railscasts. I would like to know if there is a way to mail the "rails private error page" to someone when something goes wrong, and show the user another message. It should be possible to do in the rescure_action_in_pulic, if I knew how to render the rails exception page...

Cheers!

Yes you can. The full exception can always be found in the variable $!

The exception-notifier plugin is a REALLY great way to be notified of exceptions (...) in production mode.

http://dev.rubyonrails.org/svn/rails/plugins/exception_notification/

@Mahmoud Actually the ruby rescue system can be used in that way basically the rescue_action_in_public just gives you a chance to catch exceptions outside for all actioncontroller code

you can do a rescue block for specific errors or all error within a single action or in a begin-rescue-end style block for a specific portion of code

so

<code>
  def some_action
    ..code..
    begin
      .. something that goes wrong..
    rescue
      .. to the rescue!..
    ensure
      .. Always do this!..
    end
  end

</code>

or

<code>
  def some_other_action
    .. stuff that might go wrong ..
  rescue SomeSpecific::ClassOfError
    .. rescue for that case ..
  rescue Exception => e
    .. General error of any sort ..
    .. e is the class of exception ..
  end
</code>

@xajler, I have done some episodes on authentication and authorization in the past. You can see them here.

http://railscasts.com/tags/9

@Mahmoud, sorry to disappoint. I considered touching on the "rescue" statement, but this is more about Ruby than Rails. Maybe it will work though.

Thanks Ryan, anybody knew how to upload file using attachment_fu plugin.Ryan, will you make one?

As always another good tutorial. I always like it when I see another video available. Although I am falling a little behind in trying to keep up :)

Thanks Ryan

anyone know how to show the process name as the tab title in iterm like in the video?

to answer my own question, i eventually found this: http://xanana.ucsc.edu/xtal/iterm_tab_customization.html

i don't think i'll be using it though, seems too hackish and does some weird things when sshing.

@vlad, I just edited the title in the session information panel (command-i).

ryan, i meant automatically.

now this works like this:

http://rails.learnhub.com/lesson/page/6392-action-controller-rescue

class ApplicationController < ActionController::Base

  rescue_from ActiveRecord::RecordNotFound, :with => :record_not_found

private

  def record_not_found
    render :text => "404 Not Found", :status => 404
  end

end

Thanks for showing us how to handle this irritating error.

Just for the sake of new visitors, Rails has changed quite a bit during the last 4 years. Here's how you could do it now:

class ApplicationController < ActionController::Base
  protect_from_forgery
  rescue_from Whatever::Exception, :with => :whatever_exception
  
  private
    def whatever_exception
      # do something here
    end
end

Here's some basic guide (official)

Does this work well on Rails 3? I doubt it. I changed RAILS_ROOT to Rails.root. But, it doesn't work yet.

This doesn't work anymore in Rails 4.2. Instead, use rescue_from.

Example:

class ApplicationController < ActionController::Base
  rescue_from User::NotAuthorized, with: :deny_access # self defined exception
  rescue_from ActiveRecord::RecordInvalid, with: :show_errors

  rescue_from 'MyAppError::Base' do |exception|
    render xml: exception, status: 500
  end

  protected
    def deny_access
      ...
    end

    def show_errors(exception)
      exception.record.new_record? ? ...
    end
end

This episode has been updated for Rails 5 as a blog post. Handling Exceptions in Rails 5